Last year I posted a rant about how poorly club coaches typically handle multiple keeper situations. It's true that at the older levels, particularly the last two years of club, you rarely see top level teams with a single keeper.
My kid was the only keeper for the vast majority of her youth career from U11-U16. Her last two years, U17 & 18, (ECNL) she had to share time, although measured by playing time, she was still the #1. In her last season, there were even 3 keepers on the team. All 3 were excellent, roughly the same level of player, but with different strengths. As it turned out with injuries, ACT tests, etc., the team never had all 3 in uniform for a single game. So for sure, a top level team is always going to strive to have at minimum 2 quality keepers.
My kids' coach did an admirable job keeping them rotating as far as pure minutes goes, but I always wished that he had handled it a little differently. He let them work out an alternating halves schedule, and then every now and then, when his gut told him to make a change in the pre-arranged schedule, he would. In my opinion, a keeper needs to know their role and prepare for it. Instead of rotating and changing up who is the starter and who is the finisher week to week and deciding this just before the game, a keeper needs plenty of advance notice and prep as either the starter or the finisher. Or better yet, designate one for an entire game and alternate games. Because the mental state of mind of a keeper is the most critical psyche on the field to ensure is in the right place, you've got to have lots of prediction and advance notice. If you know you're the #1, or you know for sure that week you're the #2, it allows you to prepare yourself mentally for that role in the best way possible. Several times, her coach adjusted on the fly, usually to the benefit of my daughter's playing time, but every time he did, it kind of wrecked the other keeper and made my daughter have to re-frame her expectations as well. To the coach's credit, his calls in that regard ended up paying off in a win, but it also brought some negatives because it screwed with the chemistry. I'm not sure if that's a big deal in the boys' game, but in the girls' game, team chemistry is HUGE. The biggest factor for success in splitting time is if the keepers get along. If they don't, it will suck. If they do, they can be a support system for each other.
As others have said here, the way a defense reacts to a particular keeper is an important and, IHMO, the most underrated quality of a keeper. Warning, brag ahead... My DD's defense always played better with her in the pipes during those two years of splitting time. The other keepers could do some things athletically that mine couldn't, and always looked more amazing in warm ups. But the team's record with each in goal spoke for itself. Luckily for my kid, our coach recognized that and when it came to crunch time, usually gave her the call.
Interestingly, I found that splitting time did not really affect the recruitment of any of the team's keepers very much. There were a couple of times in showcases where a coach recruiting one of them showed up for the wrong half, but other than that, all three got exactly the kind of looks they needed to get recruited. Ultimately, they all ended up where they were meant to be and were better for the experience of sharing time and learning how to navigate the ups and downs together.