I sort of expect any child over the age of 3 to start needing to decrease their sleep. However, I keep them napping until they naturally outgrow it or a parent asks about it. Under 3, I say that they need to nap and I won't wake them. Over 3, I do usually agree to wake them after an hour.
I've really only had one mom who asked about this and I think it was because she wanted her tired earlier in the evening!!! LOL She napped well here and would nap the full 2 hours (eventually it was just the hour because I would wake her) but mom said at home she would no longer nap on weekends. Mom even asked if she could have her ipad during the 2 hours and I said absolutely not (I'm pretty anti technology for young kids though). They pulled her out for full time preschool shortly after that and I have a feeling this played a part into it because the mom was quite annoyed with me.