At the charging rate for these bikes, you would have to ride for about ten hours (edjumacated guess) to get a full charge on the battery. And of course, every time you started it that would pull a significant amount from the battery so yes, a good initial charge is critical.
It takes much less time to recharge the starter loss from a fully charged battery than it does to charge a dead (or minimally) charged one.
Mine has however, sat for up to four months at times while I was incapacitated for one reason or another and started just fine without any maintenance charge. Of Course that could be partly due to the climate.
Put a full charge on the battery and realize that it will take approximately 20 minutes of riding to recoup the loss from starting.
