Depends. If you are just playing for recreational fun, then play whenever suits your lifestyle the best, remembering that if you have a family, they should always come first in your priority list. If you want to take poker more seriously and if your schedule permits you should probably try to play on weekends whether it be live or online. I found that especially live, playing on Friday and Saturday evenings or nights, there was a much better chance that you would be seated at a table with a player(s) who had been drinking too much, were inexperienced players and/or were on very little sleep having partied or even played without sleep for 24 hrs or more at a time. This makes them easy targets to the benefit of your pocket.
The main thing is your readiness to play.
