The good news is the internal battery is an APS3, which is the same battery the Pulsar Axion monoculars use and it's the same "extended" battery that you can use in the Thermion as the 2nd battery under the top turret cover. Pulsar already has a plan in place for replacing the internal battery should it ever have a problem, even after the 3 year warranty period it will be something they can do for a fee. This will be serviceable in the US.
The Thermions are recoil rated for up to .375 H&H, 12ga. and 9.3x64.
I agree with DNS on upgrading from a Trail. Unless you just really like the new scope design and/or want the
latest modern scope or you need more magnification than your Trail has, there is nothing wrong with sticking to what you have. I've had several customers decide to upgrade to the Thermion from the Trail because their Trail still has a high resale value and it's an easy time to sell or trade-up into a new model. But if you're happy with the Trail as it is, I don't see a big reason to run out and buy anything new tomorrow.