I have heard a lot of opinions about why back-heavy setup is bad, but it always felt like they were a bit too theoretical. While most of the concerns are probably true, it seems they are pretty negligible compared to other factors, so I'd say - enjoy what works for you. Just maintain your bike well before going on an adventure. Check the spokes tension and the tires condition.

Ideally, weight should be distributed equally or towards the center (aka triangle). But if you've got a choice between back-heavy and front-heavy, go for back-heavy. It doesn't affect steering, makes the ride more comfortable and is generally safer.

Just keep up with maintenance and you'll be fine.