Are you a day trader?
If yes, how long do prefer (limits) you keep a coin until you sell it?
I stand in both as a day trader as well as a gardener.
It all depends on the condition of the price at least i don't lose and get a profit of at least 10%.
If yes, how long is the best time to HODL a coin (6 months, 1 year etc)
I do them periodically within a span of time (3 months) only.
Many people think that BULL MARKET will came in APRIL / MAY. Are we close to that? With present BTC situation... (and all altcoins)
Yes April is very close but the likelihood bitcoin will be growing in June because at that time people will experience oversold.