Unless you know when a battery was made and how long it set on the shelf...it is hard to know how long it may last.
I've had to put TWO in my DT in the last year. Last one was free from the dealer , as it was less than a year since they replaced it last. Not sure what they put in , but- told me it was a more powerful one (hoping it would last longer ) .
I'd like to invest in a Lithium Ion, but- will wait , as I would also need a nerw charger for it.
Good luck !