I've just taken delivery of a Schmidt dynohub as my primary energy source (back-up is the old S6 sidewall dyanamo I've been using for 12 months). I've been hanging out for this little beauty for a long time (and beautiful in craftsmanship it is for sure).
Match the Schmidt it to one of the new E6/Bisy lights or an Ovalplus, and you'll have reliable light with almost ideal spread and you won't have to worry about batteries dying or having to be recharged. The lights also are effective in alerting motorists to your existence. Just take a spare bulb to cover yourself.
If your other bike has the same sized wheel you can interchange between the two without too much trouble.
Only problem is cost and source -- around AUD$350 including standard Lumotech light ($25 upgrade to Ovalplus), and they are imported into Australia, I believe, only by St Kilda Cycles in Melbourne. Plus you'll need to get the wheel relaced with different-length spokes.
The problem with commercial, off-the-sheld battery lights is not the system design necessarily, but the lousy charger that is supplied. If it is not a smart charger, then no amount of care in calculating recharge time will help extend battery life. It's even worse if you are forgetful and leave the charge on for an overly extended period. Welcome to cooked batteries. It all has to do with the crystal structure inside them.
Sealed Lead Batteries (SLA) are a good way to go if you can connect it up to your old light system. Again, a smart charger specific to SLAs is needed, but SLAs are generally much more resilient. Their only drawback is weight... but for a guy who loves wind and hills, a little extra weight should mean nothing.