25MB should be enough; that's a lot more than 2.5MB.
I suppose it could be your ringtones or themes or some other program that is trying to startup and can't. Maybe look in the log?
I had a similar problem with long boot time on my old 7230 after I did a system software upgrade.
Wiping it and doing a fresh install solved that problem and seemed to work a lot better than upgrading the existing OS.