If distance in miles is what makes you happy, great!
Like Tangentgirl, I wondered if you enjoyed your ride- since you didn't mention anything about that.
Me, I'm a slowpoke who decides on her ride based on how much time I want my ride to last that day. I stopped using a bike computer last year because I no longer care so much about how my mph. We are all different.
Actually, it's pretty convenient when you typically ride 10mph (we have lots of rolling hills here)- because I know if a ride is 25 miles long, it'll likely take me 2.5 hours.

That said, I do still brag about my longest (70 mile) ride when folks ask me how many miles I ride. Afterwards, I'll add something like "But that was my longest ever ride, today I'm only going ___ miles."
I do feel proud that 5 miles used to seem like a 100 when I first started out, and now 50 miles seems like 100 to me. At 57 years old, I'll take it! lol!