Long options decay. VIX can remain at low levels for a long time while you watch your investment fade away. As regards short options on VIX...don't...ever, never. Good luck.
Erm, yes, this is a variant of that wonderful foolproof strategy known as "buy low, sell high". We would all love to always buy low and sell high (well, I sure would). However, there's lots of devils in the details, especially with options, which makes this easier said than done.
You have to be Super right on your timing, within your given time frame. -- to trade options successfully , It's not enough to just simply place a directional bet. This can both work greatly to your favor, and against it...if you know what you are doing, or don't know. Options are a different ballgame and animal compared to more traditional investments, or trades, or bets.
Super long term options... they don't move much in IV. VIX is derived from the 30 day maturity options. So, they move the most... since your daily volatility can move from almost none to a lot. But a 2-year option is calculated with the IV over 2 year forward from now. So... while the 30 day atm IV can easily go to 30 or 50 even... the 2 year atm IV will probably stay between 17-25. And it will only go to the top end if the elevated volatility is expected to stay for longer than just a few days. I can't remember what the 2 year ATM IV in the index was doing during GFC... but it wasn't much higher than 25ish.
The confusion arose from the OP's post which speaks of the VIX in the headline and of buying long term options without explaining he wasnt referring to buying long term VIX options. The fact VIX options are European certainly has a lot to do with many things but indeed nothing with a question regarding long term non-VIX options.
The VIX tends to be quite volatile and hence if you are long the VIX you would be delighted to see a large spike such as the one on March 2nd of this year. However two things work against you in those cases. First as the previous poster remarked the actual move of the option price can be dampened simply because the seller knows you cant force him to settle by exercising. I will concur that this is not so different from regular index options in European style though I would say that the VIX is more volatile (which sounds really weird to say than the indexes are. More fundamental problem is the spread of VIX options during a big spike - they widen fast as sellers know that spikes are likely to average down quite quickly. In really So you may be on the right side of the deal but not be able to close your position until the VIX has returned closer to the mean. Again if you had American style options this could not occur in the same manner because you'd simply exercise.This effect is so pronounced that I have read in some books - like Jeff Augen or Kerry Given 's books - that its better to sell puts if you are bullish on the VIX because it grants a better ability to get out to make use of a spike. Both authors indicate that even then you should not expect to be able to get anywhere near the top end you would have with an American Style option. Of course if your timing is perfect - i.e. a day option - then you would not have this issue. However timing the market is impossible as we all know.
It's a common beginners mistake to think of options the way you are. While it makes intuitive sense at first blush it's actually completely wrong. TLDR the only difference between the price of a european option and an american option involves stocks with dividends where early exercise is optimal, otherwise they'll always price exactly the same 100% of the time and it's never optimal to exercise an american option early. Longer story, options prices are completely based on the volatility of the underlying. Do a deep dive on Black-Scholes for the basics of this. Also take a look at put-call parity, in general options aren't reflecting a directional bias in the market until you look at issues like convexity of the curve which is pretty far beyond where you're at. I'd strongly encourage you to hit the books on options pricing, as I frequently recommend there are some great finance 101 MOOCs out there that are free and taught be the best faculty in the world. I had an understanding of options much like yours and absolutely loved the finance 101 course I took. I found I'd unnecessarily reinvented the wheel deriving 50% of the info I knew, 50% of what I thought I knew was some shade of wrong, and there was a huge amount I didn't know I didn't know.