My daughter likes Hawk Sauce straight out of the mailbox. I tend to prefer bakery/creamy/custardy eliquids, and for me they all taste better after a couple of weeks steeping. We also enjoy the GWARY4, Jizmoglobin, German Chocolate Beefcake and Bloodbath right away - the GWAR line comes with some steep time on it already.
Best suggestion I can make to you is to try the eliquids that you order as soon as you get them. If you like them as is, go ahead and vape away. If you are not quite satisfied, let them steep.
Remember to shake the bottle before you put the eliquid into your tank or carto.