Yep.
If you were to ride the bike many times without using power from the battery then theres a possibility that the battery would overcharge without a charge regulator as the battery will be charged all the time, even when its full, but if your using power for lights and ipod etc then its not going to get full for long.
If you were to go on a long run without using power you could just pull the plug on the dynamo, or put a switch inline.
The other way is to build a charge regulator, thats going to involve some reasonably complicated circuitry (depending on your skill level), however it probably isnt necessary.
On the first couple of runs check to see if the dynamo gets warm, they usually self regulate so shouldnt do.