Having played for a mere 6/7 years Ive found that the pure "roleplay" of silly voices and exaggerated actions to be "IC" have subsided with age. When I was younger we were all very RP heavy with voices and characters, acting and shouting and crazy stuff.
I think that as a group matures TOGETHER people tend to drop the theatrics, after 7 years we have all done all the silly voices we can, we have been through ccampeigns where the paladin decided to try to kill my Quasit familiar becaus ehe was a paladin and the thing detected as evil, or played mages with 12 hp because low con was ic and then died every session. I think the nature of such games is there really are only a few character types and once you have played them all out people become much more.. mercenary.
The campeign we ended just tonight is a good example, the whole campeign was a city of thieves setting where we were hired out by a guild to do various jobs.
We often had 0 combat sessions, 3/4 of them, but I wouldnt call them roleplaying, we all played our characters as professional fighters. REAL mercenaries dont have silly voices and flamboyances. Anything that makes you stand out tends to make you a target, we would spend 3-10 hours caging houses, doing research on people and information gathering before each job. Forming plans and aiming for military precision. Our intereactions with other pcs would be role played, but tey would be very simple, affairs, challenging and enjoyable, but with an aim and purpose.
Oter sessions could be just one long extended combat. several sessions of nothing but a long complex crawl were not unusual. We never really tire because of the jokes, comments banter, and other comments throw about the room in more relaxed moments, other times the room was silent but for the roll of dice. I think this campeigns light point was "The scarlet paladin", a house of ill repute that one character liked to frequent, from that point on the fighters sexual orientation was up for all sorts of snipes which kepts us laughing
I think I would agree with the idea of 70% tension, 30% relaxation over trying to measure out roleplay and combat as if there is a magical "perfect" mix.