This is not long enough. You can say whatever deadline you want on your invoice, but in reality it will be paid approximately 30-120 days after it gets received by the person responsible for paying invoices at the company you work with.
> two weeks later i’m refreshing stripe like a fool
This is still definitely not long enough. Also, Stripe is extremely risky. One chargeback and you can lose a lot.
> just trying to see if this pain’s real enough that people (like you) would drop around $49/mo for it
No: Invoicing/billing/client contact info is the most important data a small business should keep secure. Further, I would never let an automated system reach out to valued clients on my behalf--ever. I have high standards for apps I give access to my financials/P&L/client list and it would take years of trust and reviews before I'd ever consider something like this.
> i just need to know if this is a real pain
It sounds 100% self-inflicted and easy to solve. If you want to be paid the second work is over, use a system where the funds are escrowed and released upon client approval of the project.
Otherwise, all you need to solve your pain is to build a 90 day runway of funds (at least) so your clients can follow their standard processes for invoice payment.