There's not much reason for it to slow down at the moment... I'd just recommend going to a reliable broker-dealer who can help you make safe, long-term investments rather than trying to play the market. That can result in great rewards if it goes well of course, but a more steady approach yields substantial results in time with far less risk.

There is no limit because inflation exists, so even if a company stays the same in real terms the numbers will increase i.e. $100 in 2017 is only worth $98 in 2016.
Also the dow jones will always go up over time because of how it is 'rigged', eg if a company performs really bad its dropped from the dow jones and a new bigger company takes its place

Don't try and time the market; that's for amateurs. You want to be making investments in a responsible way e.g. 401k where your investments are diversified among various stocks and some bonds through mutual funds. No one can predict the future, but it's hard to beat the S&P 500 that's for sure.

Personally, as far as cryptocurrency I have some bitcoin, ethereum, and maidsafecoin. I only have confidence in bitcoin going up, while ethereum has the opportunity to do well and maidsafecoin could just as easily belly up as reach the stars.

Never invest more than you're willing to lose in cryptocurrency since it's highly volatile. The stock market is a much safer investment which is why the bulk of my assets are there.

Nobody has any idea. Anyone who says they do is full of shit.

With that said, I largely agree with the previous commenters. Crypto is just gambling, so be prepared to lose all of your investment. Don't try to time the stock market, and don't try to pick stocks unless you're going to put in serious time studying. For nearly all retail investors (you, me, and probably everyone else here), index funds, or other mutual funds or ETFs with very low fees are the way to go.