Background: DD is 2.5. Her nursery is (roughly) organised in two groups per (eventual) school year so in her case the "older" group for her year are born from September through to, roughly, early March and the "younger" group are born from mid-March through to late August. DD is therefore virtually the eldest in her class (there are a couple a week or two older, but they only do a couple of mornings a week). Back in September when she started this class the room leader suggested that she would really be better off in the class above (i.e. the September-March class), and we discussed that briefly with nursery management, who said that if a place came up in the older class they'd offer it to us before turning to the waiting list. As it is, DD has done the whole year in this class and IMO it has worked out well she is obviously ahead of the youngest children in the class but I don't think that's a problem, and she has formed friendships (or 2yo proto-friendships, anyway) with many of her classmates. Specific things I was concerned about (e.g. potty training without having older children to copy) actually went like a breeze. And being the oldest does give her a certain amount of freedom to exercise her bossy tendencies 
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At the start of next week all the children in nursery are moving up to their classes for the next 12 months; her class are effectively moving up as a block and they've been having settling in sessions in the new room and spending time with the new teachers for several weeks now.
Today I got a phone call from the nursery owner/manager saying that a spot had opened up in the next class up (i.e. the September-March class) and DD could move straight up to that class if we wanted, instead of going up with the rest of her current class. I said no, on the basis that she is happy where she is, has friends in her class and has been preparing to move up with them -- suddenly sticking her in another class on Tuesday (although the children do mingle, so it's not as though the other children and staff would be completely unfamiliar) would be confusing and difficult for her.
Then I called DH to run through it with him and was surprised to find that while he didn't think I was wrong, exactly, and isn't suggesting I should call back and change my mind, his instinctive response would probably have been to accept the offer and put DD in a more "advanced" class.
So -- was I right? What would you have done? Be gentle with me...