After the positive response to my original post I have gone through my whole gear list and completed my report now. Here are some observations on the rest of my gear:
Clothes: Here is some good news: Clothes like T-shirts, fleece pullovers, trekking shirts and pants have a surprisingly long life expectancy. No matter whether you buy cheap no name/generic stuff or expensive brands outdoor clothes survive up to a year and more before they start falling apart. It does not pay off to invest a lot of money into brand stuff. Pants have a shorter life expectancy and survive only about 6 - 9 months before the zippers start wearing out or the fabric starts ripping. But if you have chosen a light colored (T-)shirt you will encounter a cosmetic problem first. After a couple of months of wear the shoulder straps of your backpack will start rubbing off onto your shirt discoloring it. No washing machine will be able to remove those discolorings and the shirt will always look dirty. Either chose a dark color or live with the discoloring.
Insulation jacket: I have used a Montbell Thermawrap jacket for 4 years and it still has gotten some life in it. To my big surprise the zipper has not worn out yet and the synthetic insulation is still decent, though degraded by several washes and hundreds of times being compressed into the little storage bag. I will definitely buy it again.
Socks: Socks have a much higher life expectancy than shoes and survive about two or three times as long as shoes. On a thruhike I have to change shoes about every 4 to 6 weeks, whereas socks survive upt to 4 months when using gaiters. Gaiters increase the life expectancy of socks a lot by keeping debris out of your shoes that wears out the socks (and the skin on your feet). My observations are based on wearing Wigwam Cool-lite socks in combination with gaiters. Thinner or non-hiker socks will not last that long.
Gaiters: I have used the same pair of Simblissity LevaGaiters for almost 20,000 km of hiking although I had to repair them several times. After about 6 - 9 months of constant use the lace hook will break. The problem now is to find an appropriate replacement. You will usually some sort of hook in a sewing shop and you can then sew it on with dental floss. I have replaced the hooks on my Simblissity gaiters 4 times before I decided to bury them. After 20,000 km of use the seams had come off and there were too many tears in the fabric. Considering the price and the weight of the gaiters this is a fantastic and very durable piece of equipment.
Pot: My Tatonko 1 l titanium pot is the oldest and longest surviving piece of gear I own. I have used the same pot for all my hiking career cooking in it over a thousand of times. It does not even look very battered now. After a couple of years the rubber insulation of the handles has come off but this is only a major flaw. If the pot handles are sticking out while cooking they will not heat up anyways and therefore you do not really need this insulation. Bottom line: a titanium pot is an investment that will almost last forever.
Spoon: I started out using a plastic spoon out of weight reasons. But Murphy's Law has struck several times and the plastic spoons always broke at the most inconvenient moment. Although this is not a life threatening situation it is a major annoyance. No matter what plastic spoon I bought they all broke sooner or later. I have now changed to a Sea to Summit Titanium spoon and have been happy ever since.
Wallet: My Simblissity UL wallet is my second oldest piece of gear and has accompanied my for over 5 years. I like it so much that I even use it in my non-outdoor life. Only now after 5 years of almost constant use some seams are coming off and the velcro is wearing out. This is a very well thought out and built piece of gear and I cannot recommend highly enough.
Outdoor watch: I have used a Suunto Vector for over 4 years for outdoor use and in normal life. Although the watch itself still worked fine I had to replace it after 4 years because of problems with the battery compartment. The battery is covered with a plastic cover that is held in place by 3 little plastic catches and waterproofed with a plastic O-Ring. After so many years of use the O-ring material deteriorated making it more and more difficult to close the battery cover. And while trying to force down the battery cover the plastic catches will break off eventually. This leads to two problems: The battery compartment cannot be closed properly any more and water can penetrate. Also the battery is not held firmly in place any more. As soon as it loses contact the watch will reset itself... leaving you in the middle of nowhere with no idea of what time it is. Change the O-Ring as soon as it deteriorates and always be very careful when closing and opening the battery cover.
Head lamps: Depending on how long and where I go I use one of my three Petzl headlamps: E-Lite, Tikka and Tikka Plus. Neither one of them has ever failed me. Even when changing the batteries often the plastic battery cover has never broken. I only had to replace a Tikka once after it had gotten very wet. Although it worked again after drying it it seemed to go through batteries much faster than before and I therefore decided to replace it.