Interesting to see different people's takes .... Going back August / Sept last year was regularly doing 15 miles and then went out with someone else who took us up to 24 for the 1st time .... not sure why but this jump felt huge, the worst part I didn't have cycling shorts at the time and my poor rear at the end of it and will never forget we went down a road with speed humps about 1/4 from the finish which damn near destroyed me

That distance fairly quickly became the norm with slightly longer rides going to 27/28 and then up to 34 as a max on my own one day but with most of our rides being 27/28 at weekends and 20 during the week ... all on the flat.

Signed up for the 52 mile charity ride and knew there were loads of hills so extended out to 40, then 42 taking in some reasonably tough climbs and the week before was out on my own and feeling fairly fresh so decided to take the long cut which took it up to 47 and beyond the point of no return but about 3 miles from the finish started getting some pain so ended very slowly and cautiously.
Seemed fine for the next week so did the 52 miler which seemed "OK" but the following week a 20 miler bought it back again.
It's finally settled down having had a break with a bad cold etc and the last couple of rides have been fine, I'll start building it back up but maybe the 33% + jump in mileage overnight combined with taking on hills at the same time which I wasn't used to was just a bit too much.

Really do want to hit that 100 this year and so glad I found this as a hobby as am so enjoying it along with the social side and regularly going out with friends.

Cheers for everyone's input