The problem with playtime being earned is, at least until the final years of high school and in college (when keeper skills are beginning to get rounded out) is that the keepers (unless there is a very wide disparity between them or the lower is a field player that sometimes plays back up as keeper) are unlikely to have the same disparity in each skill. For example, one keeper might be really good at 1 v 1 while the other keeper might be really good at diving. Their styles might also be different (with one keeper being a sweeper, while the other is a tall-on-the-line keeper). If the coach knows how to manage them and communicate to them re his decision, then it can be mitigated. But as has been mentioned, most coaches don't know about the position or are poor managers. The keepers are likely to view decisions as arbitrary and resentment builds (unless they are being played on the field too, which is hard for coaches, particularly as the player ages, given the specialization and given the competing demands for time).
On the other hand, for equal time to work the keepers have to be very closely aligned in their skill sets. Otherwise the stronger keeper resents having to share. The weaker keeper loses confidence being compared. And the parents begin to snipe when games are lost.
, still got too emotional during tryout season. I would try to find her a "perfect spot" on a team where she was one of the weaker field player starters, so she is guaranteed playing time while still has plenty of room to improve.
