On older pcs it cant be avoided that it takes a long time to compile vvis at normal. Thats why there is a fast option which skips portalflow.
Also, portal flow is a process that gets slower the further it is. So 1-5 can be fast (<5 minutes). 6-8 usualy get quite a slowdown on large maps (10 minutes) and 9-10 often are a pain (20+ minutes). Still, super fast pcs or more RAM increase the speed alot, even on the later parts.
For any testing that doesnt have any optimizing related to it you should use the fast option. Same for lighting, if the light doesnt matter use the fast way. It saves alot of minutes.
Also note that hinting isnt allways the way to make it faster. As you often make more leaves you add more time. However, when vbsp messed the cutting of leaves up you are able to improve it massively. Just check the portal file in hammer sometimes, bad areas are easy to spot due to the massive line clusters. Optimize it there.