It took me 11 months to create the the first release of Pocket Tanks. That included 60 weapons and two separate versions of the game... shareware and deluxe.
Super DX-Ball was in development for 2 years, and that included all the new boards plus the 2 separate versions.
If you were to add up all the time I spend making the 1.1 and 1.2 updates for Pocket Tanks, that would add up to about another 6 to 8 months of development time. If you throw in the time I've spent 'trying' to add network play to Pocket Tanks, that would probably be another 4 to 6 months of coding. (that is just an estimate, since I hate thinking about the how much time was lost on the network code)
Roughly...
Pocket Tanks = ~2 years
Super DX-Ball = ~2 years
If you throw in the expansion packs, the numbers look more like this:
Pocket Tanks = ~3.0 years
Super DX-Ball = ~2.2 years
Moving forward... network play is seeing some great progress and I have plenty of updates for Pocket Tanks planned. But to bring balance to the force, I hope to get the opportunity to update Super DX-Ball and make some expansions in the next few months.
And then there is the 'new' game that we are designing now.

(time flies when you enjoy what you do!)