The OLD beam scales had little or no damping and they did stabilize slowly but I don't know of any those being made for more than 35 years. I've never seen a magnetically beam scale require more than 2-3 seconds to stabilize ... that's close enough to instant for me.
IMHO, sweating precision charges for handguns (and a lot of rifles/cartridges) is a waste of time. Truth is, a couple tenths one way or the other would only matter if we used charges on the ragged edge of KABOOM and surely none of us would do that.
The advantages of beam scales over digitals is:
1. No concern over line voltage, stray magnetic fields, warm up.
2. A balance beam scale will last forever with no loss of sensitivity or accuracy if it isn't physically damaged.
3. Beam scales follow the changes of a powder trickler immediately. Few digitals do and that makes it difficult to trickle-up precision charges.
4. Beam scales don't "wander" during use; set it and forget it.
5. Reloading digitals (all of them) are cheeply made, throw-away devices. Electronic devices often fail and without warning.
I've been using my old Lyman M5 scale since '65. A lot of powder has gone through its pan and it still reads exactly the same as it did when new. I have one small digital I use to weigh cases and large bullets, NOT POWDER, and I don't expect it to last as long as the Lyman. (I say Lyman because that's what it is but it's not unique, I doubt any other beam scale would do less.)