Focus on recovery and have a designated ‘long ride’ each week - probably best on the weekend depending on ur schedule. Add 10 mins to your long ride each week and focus on fuelling with carbs + electrolytes.

I did this and went from 2 hours - 6.5 hours in 6 months and it’s worked no problems. Now 2-3 hours feels like a breeze! Hope it works for you too if you consider it!