I'm buying some as soon as my Ti comes back from RMA purgatory.
I consider myself a lucky Hopper owner.
Indeed a lucky Hopper owner. Thread cleaning was never a priority though they appeared pretty clean to me and I brushed out my unit often, including the threads, as well as occasional ISO baths for the standard frontend, and some ISO swabs for the chamber. Backend threads I never fiddled with much except for the occasional brushing and cleaning the contact on the backend and positive battery terminal in the main body shaft. I've never used the magnetic charger and only a couple of Nitecore chargers yet I noticed right away a few of my original batteries didn't hold a charge like some of the others. Same thing for a second batch of batteries - one was worse than the others.
I've only owned and used the standard frontend, never the PFE though I'm intrigued that it will lessen draw resistance but I won't fork over any more money to HL at this point except for batteries (which you can't obtain for another 2-4 months at best - go figure! - and I'm certainly not ordering them in advance and giving them money without receiving anything immediately in return).
With the fraiity of the design and variability of the batteries, at least early on as I haven't bought new ones in a couple of years, the Hopper does need maintenance at least over time. I'm really anxious to see how Blu Tack will work but first gotta get my unit back from RMA-ville, whenever that is.
As for batteries the more they sit unused, even fully charged, I think they lose their capacity somewhat. It's not a scientific observation but now that I have a loaner Ti from a friend I've been using all my batteries, which are numbered, and they don't last as long after they'd been sitting fully charged for some time between when I sent my unit in (September '18) and very recently when I received the loaner, and also re-charging them too after usage. And the loaner unit is in pristine condition too.
The Hopper is siimply something I love to hate and hate to love. When it works well it's great, otherwise reluctantly forgettable. Happy weekend to all.