I like both... each has it's own pros and cons
short term investment is easier, less riskier, but also with less potential profit... hit and run like you've said
longer term investment tries your nerves and is riskier...but can bring a lot of x's if you choose the project well
there are also two types of coins to be suited to each type of investment... the older, already established, less riskier coins.... and the new ones...
At this point I'm aiming to get some profit doing quick trades on established coins, like ADA, CVC, LTC, RVN, etc (not having much luck at the moment)
And filling bags of Beam, Veil, Veles, Zel, for later trading (and hopefully profit)
cheers