If we consider cryptocurrency as a whole, then the total capitalization of all coins with the passage of time only grew, which speaks of the development of cryptocurrencies. Every day more and more people learn about cryptocurrencies, growing interest in crypto. There are many services, online stores, which integrate as payment for cryptocurrency. All this suggests that the cryptocurrency will go up. But if we consider different coins separately, then I can give some examples of the growth of known coins:
LTC
27 Oct. 2013 - $ 2.25
27 Oct. 2017 - $ 55.46
24 Dec. 2017 - $ 304.03
20 Jul. 2018 - $ 87.23
Zcash
18 Dec. 2016 - $ 37.55
27 Apr. 2017 - $ 57.74
08 Jan. 2018 - $ 884.68
20 Jul. 2018 - $ 202.17
It can be seen that at various times the price has been rising or falling, but the long term has grown and this trend is applicable to most coins available on the coinmarketcap.