I never really bring luxuries on short outings other than food; like mentioned above, I'll bring some perishable stuff on short outings that aren't suitable to 4 day trips.
I live in Manhattan, and I have no backyard, so I definitely treat most of my overnight trips (which are almost all of my trips) as gear testing outings. I can wear clothing combinations out on walks in all seasons; I can load up a backpack and spend 2hrs strolling through Central Park to test fit and carry; I can try out a new stove in the kitchen; I could spend a night on the floor testing a new sleeping pad; but testing out shelters and sleeping gear in something comparable to real world conditions just isn't possible.
For a 3-season trip in non-bear canister requiring country, my base weight is only in the 6-8lb range, so throwing in a spare shelter to play with, or bringing my Nunatak Arc AT on a 35F night to see if I can push it(with my Specialist as a back-up) is not a big deal.
Heck, I'm going on a 5-night trip to Yosemite/Ansel Adams in 4 days, and I'm probably going to bring both my BPL Nano tarp (primary shelter) and my MLD Spinnaker Solomid(to play with), since bringing the Solomid only brings my base up to 11lbs,(~21lb w/consumables), and I get to test it out in the conditions I'd prefer to be hiking in (vs the East Coast). I may even bring my silnylon Duomid to use in real conditions so I can decide once and for all which Mid I want to keep and which I should sell.
I'm only planning on 15-20 mile days, so the extra pound or two won't be a burden compared to the value gained in refining my gear/skills for the future, and well, playing with gear is fun, and fun is the point of this, anyways.