Believe it or not... there is a method to all the sinking fund madness... usually taken in to account are lift, fire system and plant replacement over a 15 year period with a consideration taken on carpet replacement and painting works over a 10 year period... this is usually rolled out...
I would say that a sinking fund allowing for 80 units of 10K is a good starting point, but then again how old is the development? if anything over 5 years I would be pushing to have that increased by another 5K