There’s no time limit in the section of the Act, nor should there be. Levies in many older buildings were either skewed artificially low, to attract buyers to the larger, more expensive apartments or just lazily divided equally because there was no appreciation that a top floor north-facing apartment with a view would eventually be worth more than a ground-floor unit facing a brick wall to the south.
If there is an obvious disparity there should be no problem in getting this through especially if you can get unanimity among owners on the new splits. However, this is unlikely as some owners will lose out. The way to get everyone on board may be to make it clear that you aren’t looking to backdate the new unit entitlements – you just want a fair split going forward.
Also, if you can’t get unanimity, those seeking the redistribution will have to pay for a surveyor to provide an independent assessment of the new UEs, and then you have to work out if it’s worth the money to make the change.