I'm about 2 1/2 years out from second replacement of pulmonic and aortic valves and largely back up to speed. I ran 48 miles over two days by doing 4 miles every 4 hours for 48 hours. That's a record for me.
I just completed the Lost Coast Trail along the northern California coast with my sons. It's a 25 mile backpacking trip along an isolated stretch of beach. https://www.wonderlandguides.com/hikes/king-range/lost-coast-trail
We took four days to do it and all survived - yay! The uphills are hard for me but luckily there is not a lot of climbing on this one. It's just a lot of varied terrain along the beach - boulders, cobbles, bedrock, loose pebbles, and some surface that is stable. We left a vehicle at the beginning at Mattole in case we needed to turn back (people usually hire a shuttle to get to the start and leave a vehicle at the end). It was my 12- year old son's first backpacking trip and he did great - better than me on the uphills!