let's see, I've had anything from pixies to really long hair.
In terms of maintenance, I think all hair styles require a certain upkeep regardless of length. When I had my hair shorter, I could not go without a haircut for more than 3 weeks. If not, I would look unkept. I have natural wavy hair so when I sport a shorter haircut, I need to blowdry my hair everyday.
I have a layered cut now, well past my shoulders. That requires maintenance too, coloring, frequent trims etc.
I guess my point is that hair length has little or nothing to do with how put together you look. It is the condition of the hair what matters.
In regards to how "acceptable" it is to have long hair past a certain age, I have strong opinions on the subject. I'm still in my 30's (36 to be exact), yet I refuse to go by some societal rule that tells me that when I turn 40 I'm supposed to chop my hair off, start wearing certain clothes etc. Why?
I think we should stop being so hard on ourselves...