I've been PBPing on the DFRPG site (I think it's paranetonline these days) since 2010ish? I think my longest game started in 2014. There's one game I'm in that a single scene took close to a year. I don't get it. I, sometimes, feel that my posts are the only thing nudging the games along. Generally, I like the slower pace of a pbp to make decisions but, if posts happen too infrequently, it's difficult to remember what is happening in the game or even remember the personality of your character.
There was only one time that a combat was taking forever - MONTHS - to complete so we got on discord and hashed it out in a couple hours just to move on. This has only happened once.
My primary tactic is this: If I don't have time/energy to do a big post, I'll post dice rolls and a quick explanation - even a couple sentences - just to keep things moving. I might go back later and fill it out when I have time (with the GM's permission). or let the GM narrate the results.
Ghosting, I don't understand. I do, sometimes, wonder if people have died. I've had several long-time, consistent posters just stop to never post again. Which makes me sad.
For one game we set up a discord server just to take on a lot of the OOC stuff. This has been super useful for the slow, occasional posters. You can hash out decisions, answer questions etc... very quickly and then get your post up.
In the 2014 game, the GM is very good and giving us good hooks. 'This is what's happening in this scene, what do you do'. While it feels railroady, it's a FATE game so it's easier to throw compels at players and the GM has a good idea what we want to do because of Aspects and what-not.
I've never played a pbp D&D