I agree with tsl, most of the returning first and even more, rides are far beyond what I managed to pedal when I got back on the bicycle after a lot of health issues, for 25 years. I was managing to eke out 2 miles a day, 5 days a week, and felt like I had been in a marathon, or maybe a nice long forced march. It took me a bit to get my fitness where I could do the mileage I now am capable of producing, but it was worth all the effort to keep at it.
As so many said above, just ride what you feel good at doing right now, let your body tell you when its time to increase. the long rides will come to you, if you stick with cycling, and not by spending a fortune on a bicycle, although that can be fun
, too.
Bill