All of these would work, depends on what you are trying to do and what kind of event caused volatility. You could simply short a really long dates straddle (e.g. Dec 13) - it's pretty much pure vega assuming you deem the implied vol levels high enough. Long-delta 1x2s or put trees on VIX that show good break-even levels is a reasonable way that will not break the bank either.
Anyway, I'd say the farther you go, the better, assuming the vol is rich enough - e.g. Dec13 or even Dec14. I had some long vega positions and liquidated some Friday. Given that long-dated vega does not really decay, it makes sense to buy it when it's cheap and sell it when it's rich. PS. Not gonna comment on the actual positions now - asking this kind of stuff of an institutional trader is like asking a girl on the first date if she wants to sleep with you.
I forgot about the long-term short straddle. what I'm trying to do is a long-term mean reversion of vol. For short term short vol trades, I can and have done several different types of positions. But I don't know the best way to do long-term/indefinite mean reversion. If I thought JPM would eventually get back to 40, I could buy JPM and simply hold on to it indefinitely as a long-term trade. If VIX were at 35 and I thought it would eventually go back to 25 but don't know when, how would I trade this? All the VIX products are based on futures, which are specific time-framed. Maybe going out as far out on options (like your DEC13), but when VIX > 35, there might be backwardation and the IV might not be as elevated, but it will still be elevated. Sorry for my rambling.
Ha! Apologies, I forgot you were an institutional trader. I was simply implying if you had any positions not what positions. Should have made that clear. As for the date issue, you'd be surprised (I'd say a 10% chance is quite high). Girls behave like guys these days. It mostly sucks because although (a plus point for guys) they're more willing to sleep sooner, they've also lost the ability to dress well. Sexy isn't. Every time I see someone with leggings and butt not covered, I cringe! Back to vegas...