When I was hanging out at the local hi-fi fixit shop, Mark gave me two old suitcase-style tube testers; one a Heath, and the other I can't remember, but a good brand.  I hadn't used either of them more than a few times when they started to go intermittent on some sockets and tests, and then bad. I opened them up, and was horrified to find that all the solder joints in there were gray, crusty, granular.  You gotta dig that there are literally hundreds of solder joints in a commercial tube tester.  I got my nine-pin socket working again for some tests, but ultimately, those things defeated me and ended up in the big brown file cabinet.  I've also seen the same thing in a lot of old tube hi-fi gear I'm pulling apart - horrible crusty solder joints all over the place. I don't know if that was specifically Kester 44, but certainly an equivalent.

I've been using first the old RatShack and then Cardas for about fifteen years now.  I take that gear apart, and those solder joints look just like the day I put them in there.  A lot of my gear is either made on commission or sold after the fact to appreciative pals, and for the difference in cost (maybe two bits for a piece of gear), I just can't conscience the supposed economy.  These guys trust me.

It's certainly your call, but that $20 half pound of Cardas will last you for years (probably your career as a hobbyist) , and you'll never have to think about it again.

Respectfully,

Poinz