Depends on the ammount/size of memory you have installed, and the kind of applications you're running.
An unexpanded 16MB Fast A4000, won't last long surfing the internet and doing other stuff simultaneously.
With 152 MB, I go till some proggie halts the system (won't go out of memory with the usual apps running -expect large files/compression/compiling etc.-).
OS4 will resolve these problems, hopefully.
