As a counterpoint: I have the opposite policy for refunds, and have for the last 8ish years. The official version, to satisfy my accountant [+], is a full refund with no questions asked for 30 to 60 days. The unofficial version is that I will give anyone a refund in (basically) perpetuity. I think my current record is 70 months after the transaction.
My refund rate for BCC is 2.7%. That's the easiest one for me to calculate with a single SQL query. Don't hold me to these, but I think AR and my other products are at about 1% and 0.5%.
Refunds are a very easy way to amicably part ways with ex-customers who are not good fits for you, rather than having the resolution where a) they can't use your software and b) they feel like you've stolen their money.
Refunds quickly remove problem customers from your inbox. This will save you time and, more preciously, sanity.
Prominent money-back guarantees frequently increase sales in a statistically significant fashion across your entire company. This is one of the cheapest A/B tests to implement, by the way, since you can create a guarantee by adding two sentences of copy.
Most customers have a fully functional put option on your digital goods, brokered by their credit card company and assignable to you instantly by saying the words "Internet merchant" and "chargeback." You should prefer that customers resolve disputes amicably, via refunds, rather than aggressively, via chargebacks. Chargebacks come with aggressive fees ($15 to $25 plus the purchase) and accumulating too many of them can get your merchant privileges revoked. (This is about the point in the post where somebody is going to suggest adopting Alpha Black Lotus Depository Certificates, which they believe to be superior to credit cards because ABLDCs don't have chargebacks. This is a moot point because your customers don't possess ABLDCs, but be that as it may, charebacks are net welfare enhancing for merchants because, like generous refund policies, they encourage transactions.)
Refunds will not typically meaningfully impact your cash flow in a digital goods business. You probably have stupendously high margins -- they absorb refunds as a cost of doing business quite easily. You can implement a rolling reserve on yourself [++] to cover them -- mine is $500, which is more than adequate at a revenue figure in the six figures.
+ Your accountant may not be happy if you sell goods with perpetual characteristics because it makes revenue recognition more complicated than it needs to be.
++ Rolling reserve = "Don't spend the last $500 in the checking account", which is good advice for a host of reasons, not the least of which being you'll never worry about refunds impacting cash flow.