I grew my hair from APL (unstretched, summer 2009) this year to a lil past BSL (current, unstretched). It has helped significantly with growth retention, because I'm not manipulating my hair, and I also don't have to trim because its mostly braided underneath wigs and LF's. The benefits outweigh the risks for me (of not letting hair breathe, as you stated).
I only wear my wig when I'm leaving the house. If I'm at home, its OFF! I have on a satin scarf instead. When I do wear my wig, I have on a mesh wig cap (not a stocking-type cap) so that my scalp and hair can further breathe. This also cuts down on scalp sweating, if its an issue on warmer days. (My scalp rarely, if ever sweats, but the mesh cap just feels more comfy than the other type). The mesh cap is a little more costly ($1.15-$1.20 vs. $.99 or less), but definitely worth it!
I am past BSL and growing, I have comparison pics of b4 I started consistently wig wearing again to a couple months later in my Fotki (dated Nov. 19). I'm transitioning, and the wig being a nice style without me having to fool with my own hair is so relaxing. I don't have to worry about looking presentable, and its a great way to change up your look!
ETA: I've been wearing a LF during the above mentioned period, but don't use adhesive, so I can remove it as soon as I get home. I secure using bobby pins at each side burn in the front. This prevents lifting...the rest of the lace/wig edge is flush with my head/edges.