I don't use paste solder very often.....but when I do I need it VERY
badly. Makes me nutso when I dig among my bench drawers to find
that long ago stored tube of stuff, which is now stiff with age!!!!
(My whine: "but I just put it in the drawer a year ago"!!) Now
useless. Go buy more of the same , UGH !!! Last year, in doing some
trading of supplies, a buddy of mine came up with what she claimed
is a non-hardening, paste solder. I bought a selection from her.
Impressive!! (And nothing much impresses ole Bubba here.) Now when
I go digging for it, it's still soft and usable. Try it, You'll
like it!!! And tell her I sent you.