WOW, trying a big interior (London Natural History Museum Grand Hall - CGTalk lighting challenge).
 
Got up to 22 light sources, before V7 wouldn't take any more - in radiosity render and spectral light type too. Very impressive! Never tried more than 8 in V6 and that was often a struggle.
 
Still had 76% resources as well, even with that big museum model. Had 1 sun, 10 spots, 11 quadratic omnis.

Totally stable for all of my 6 hour's work, until I tried to add that 23rd light.