I'm confused, when I see the word "trail" I think of unpaved off road trail requiring a MTB, crossbike, hybrid, or touring bike and would be unsuitable for the typical road bike; when I see the word path I think of a paved bike path, so I'm not sure which you want an answer for. Some trails are questionable because while they may not be paved they used crushed limestone and shale that can be ridden easily with a road bike and seem more like pavement then not, so not sure how those would be classified though they call them trails.
Be it as it is, I did get to ride the Muncie IN trail(?, again it's paved not sure I would call it a trail) to Richmond IN which is about 45 miles this summer. I took the bike in the back of the pickup truck and went to Muncie, from there hopped on the bike with my gear on it hooked onto the Muncie trail and rode that into Richmond, stayed overnight in Richmond at Deer Ridge Campgrounds which was a lot cheaper than the KOA campground that wasn't to far away and had to take some county roads to get there, then the next day I headed back to the truck.
Last year I did the Kal Haven trail in Michigan. That one is a crushed limestone shale trail which like I said is very much like pavement so again the question I have about trail vs path. That one my wife and I were doing a camping trip with the trailer and spent the night at South Haven Mi, so I rode the trail to the end which was near Kalamazoo, then I went back in the same day. That one was about 70 miles round trip.
Anyway those are the longest trails/paths I've been on. I have never been on a real off road trail for any distance, there were some non official trails in California I've been on, but I don't think I ever went further than maybe 8 to 10 miles since they were kind of rugged and had to be done on a MTB and that bike didn't have a computer so it could have been less but not sure because the going was very slow due to the trail conditions.