I am picking up my Avernus campaign a game year after the PCs saved Elturel. In that year some world building stuff has happened but I also want to let the players engage in some downtime type activities. But a year is a long time.
How would you handle a year of downtime? Would you let PCs retrain, buy and sell items, make fortunes, etc?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.