Definitely a mature approach, and it's definitely better for Balanced customers to have a migration plan. However, I don't think we can assume that Balanced "[left itself] enough runway to look after [its] customers" or that the primary motivation is maturity.
Balanced may have offered to sell their customer base to Stripe (or sell the company to Stripe, which presumably was refused). If Stripe accepted a deal to purchase Balanced's customer base, then it might have provided as payment, in part, an injection of cash to keep Balanced running for 90 days to implement the migration and hold up their side of the deal. Balanced might have suspended operations already if not for the hypothetical cash payment.
I'm not saying it would be wrong for Balanced to make that decision -- it's certainly better than shutting down! I'm just pointing out that Balanced may have other/more complex motivations for doing this than maturity, altruism, and leaving behind a good legacy. Balanced might be equally looking after its own shareholders by selling its (perhaps) most valuable asset: the customers. (The value of that asset crashes once Balanced ceases operations or announces its intention to do so, since its customers will immediately move to a competitor. Thus, this asset can only be sold while Balanced is still operating.)
I have no data - I'm just speculating. However, would a responsible board allow a company to continue to operate and burn cash for 90 days solely for the purpose of migrating customers to a competitor, and taking further losses in the process, when it could shut down instead and disburse its remaining assets to shareholders and creditors? (I do not intend to cast asperions on Stripe or Balanced. There's nothing wrong about this if it's what happened - it's rational and in everyone's interest.)