I haven't had any unusual maintenance issues on my BF NWT (in fact, I have fewer than I do on my road bike). This is probably for two main reasons.

1. Because the fold is relatively large (a disadvantage in certain situations, of course), there are fewer issues related to the folding mechanism (i.e., folding doesn't involve the seatpost sliding; there is no hinge in the downtube, and the handlebar stem lifts out rather than folding down).

2. I fold it and unfold it on average probably once every two weeks.