Nice job, cracking 30 miles! You are definitely on the way. You can certainly reach 80 miles by March. The question will be whether you "just finish" the ride or you "feel great" on the ride.
To avoid injury, make sure to do one week at very reduced intensity and mileage. Do that every once and a while and you will let your muscles recover. For example, if I do a 12-week training plan on my own, I take it easy during week 3 and week 9. Still riding, but very low intensity and low mileage rides.
Also, slowly add to your weekly mileage and long ride mileage. The rule of thumb is to add about 10% more mileage per week. You can go with whatever feels comfortable, but doing too much, too soon will put you at risk for injury.
Just some more tips as you really kick it into gear for the long rides. Good luck.
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