If by larger aircraft you are talking about a PA28-140 or a 172 from a C150 then I would think that 2 to 3 hours would be about right, depending on your skill level. Having trained on PA28s I was checked out on a 172 with just over an hour's flight. Going high wing to low may be slightly longer as you have more ground effect to contend with in low wing than high, which arguably makes accurate approach speed rather more critical.
Anything much bigger than this and you are likely to need a VP prop sign off