I've been wearing them almost 2 years give or take with small breaks in between I wore wigs ( 2 months )
I went from a little past shoulder length 12/09 to MBL ( currently ). I haven't had any problems so far with the previous install. I had never had a sew-in using a weave cap ( probably never will again either ).
IMO weave caps makes there be extra and unnecessary pulling on the hairline. When my hair was finished it was fine, but later that night it started feeling too tight, so I cut some of the thread to loosen it.
And to top it off, the girl who sewed my hair in asked me beforehand if she could cut my track...well I didn't know that she meant "split the track" to make the hair lay down flatter. (I'll never do this again either) because it causes shedding galore! And I paid too much for the hair ( Remy ) to have only lasted just a month. I usually can go 2-3 months AND reuse the hair 2 or 3 times.
Sorry for rambling on, but over all...I do like sew-ins because it's an excellent PS for me AND it forces me to stay out of my hair and just let my hair do it's "Thang"....grow !