It took me several months to get to the point that I can ride every day to work and not be tired. It takes me less that 10 minutes to fully recover from my 8 mile ride and then I'm fine. I go on long rides on weekends too. It'll take some time then, don't be concerned. If you feel too tired then take a break, don't push too much, it's not fun. But don't be too easy on yourself either. Take Fridays off from riding, then every other Friday. Drink a lot, take vitamins and you'll be fine.