Hopefully, we won't hit a limit anytime soon - but the ability to specify the date range would be helpful.

I also looked at retrieving this via the API. It seems to support a single date (invoice or due), but not a range and t he payments and credits API appears limited solely to a specific invoice,

What we need to do is export all invoices/payments/credits for time frame (month), that we use to create our internal reports. Downloading ALL of our data, each month then extracting the month we want, resaving, then creating our reports is what we are currently doing.