It depends on what you mean by "no dropouts". Some dropouts are tolerable...if my system is seriously being taxed I do expect to hear dropouts when I move windows around and mess with stuff. To me, untolerable dropouts are those that occur when you're just letting the system playback.
That said, my largest project so far was 25 tracks of 24/44.1 using two waves trueverb plugs (older version, which IMO is better), three or four L1 limiters, a couple C1 compressors, several odds and ends including an n-track echo, an n-track verb, and a resonant filter (
prosoniq northpole)...lots of automation, in fact almost constant automation on several tracks.
My system is a Celeron 850Mhz on an old BE6 motherboard, 256MB RAM, a couple maxtor 7200's, a delta1010, and yada yada.
That particular project totally whooped up on my system, but I could still mix. When it gets to that point I am very careful with what I'm doing and when I do it. I turn off a lot of visual effects and try to mix using the bare minimum.
Oh, and I've never once had a dropout while recording.
Slackmaster 2000