The durability is primarily determined by the DWR type rather than the fabric. DWRs, available retail, last about 30-50 miles of abrasion from either your pack rubbing on your upper body or brush rubbing against the front of your pants and lower arms. DWR life in an application like a bivy/quilt will primarily be determined by how clean you keep the Momentum90 and how much abrasion results from your use stuffing and un-stuffing.
The most durable type of DWR available to the DIYer is fluoropolymer based. Examples are: Deluge, Granger's, ReviveX, Scotchguard, or Tectron. The bivy can be easily renewed whenever you notice that drops of water soak in (wet out) rather than bead up. Key things to remember are: wash the bivy with non-detergent soap; double rinse it; spray or wash in the DWR; and then heat set it in the dryer for 50 minutes at medium heat.
The quilt's DWR renewal procedure is dependent on the insulation you used to make it and how durable the quilting technique you used is. At minimum, you can wash it as mentioned previously, spray on a DWR, and heat set the DWR with a hair dryer used on the surface for an equivalent time to the dryer.