Well firstly, don't put all your eggs in one basket.

If you are going to hold an altcoin long term I would pick a few that have some form of 'cashback' feature

eg Neo gives gas
EOS gives airdrops
Exchange coins eg KCS give trading discounts and/or profit share
Masternode coins eg DASH/MEDIC give masternode rewards

These benefits will build up over time. Also, demand for these coins should be sustainable as others want the rewards too, so the capital price should increase too