There is a consistent stumbling block that bitcoin and cryptocurrencies are viewed as a stock or currency trade which is why most people can't wrap their heads around bitcoin's constant increase in value. Retraces yes, small bubbles here and there, yes, but constant growth, let me explain that...
The Bitcoin Rise...
The thing to remember is that Bitcoin is not a stock. Bitcoin is a protocol, nothing more than a useful tool that costs nothing to use, in and of itself. Costs only come in when a) transferring your fiat into the bits on the chain and b) a small amount to transfer those bits to others(fees). We cannot judge its growth like we do a stock. Stocks are a reflection of businesses (supposedly earnings, but in these crazy times stocks are really just a popularity contest - hence current grossly inflated markets. Refer to just about anything by this guy to see the stats - youtube.com/user/TheMoneyGPS.
Businesses have limited reach/capacity. Cryptocurrencies, like bitcoin have unlimited reach, and technically (with a few upgrades which it is in the process of addressing) can service the entire planet. It's growth is limited only by the amount of people who want/need to use it (its business case can include everyone (all 7Bln) as everyone needs to transact value, and bitcoin has no borders.) There is another example of this - email, webpages, chat. Webpage/email/chat use grows and grows because its easy to use, relatively free and has no borders (china, N. korea try, but can't stop it) and so growth, unlike businesses, is quite unlimited. With $5 cell phones coming, that reach is truly unlimited.
Additionally to that list, you can get Bitcoin debit cards (Visa/MC) which I used on a trip thorough Canada/US/Mexico and back again, for food/fuel/accommodations. Bitcoin is fully spendable now with dozens of companies building bridges bridges daily.
So when to buy? Literally anytime. Dips are good but waiting for big crashes to load up, you may be waiting a long time and by then, the crash may dip down to higher levels than just buying in today. Chances are higher that the stock/housing/bond/currency markets will crash much sooner than bitcoin. Trace Mayer(www.bitcoin.kn), who has predicted bitcoin's rise quite accurately since its early days is calling for $27,000.
And these rises are just the beginning. We haven't even hit the network effect. You will know the real rise when you see massive spikes in new wallet creation. The barrier to acceptance is not spend-ability, its in individuals taking time to learn what bitcoin really is, and that is just starting to happen. Just like email in 1998 when you had to be a command line guru to have an email account and people laughed at you when you told them to start using it, and 10 years later everyone and their dog has multiple email accounts, don't you wish you could have invested in the email protocol? Email wan't designed to be invested in, but Bitcoin is. And what is more important to individuals, money or email? No brainer. That is why projections of $500k-1Million bitcoin in the next 3-12 years actually look viable and why Wall Street still cannot understand it. Well sort of. You have Dimon of JPMorgan dismissing bitcoin as a fraud, and then after the news causes a dip, buying millions. Ya, they know where it's going.