*cheers* What a wonderful community!
I'll join the crowd of mint harvesters. I found some spearmint growing rampant in my mother-in-law's back yard last weekend while we were over there painting. I miss mint tea!
Lavender -- Congrats on the window-boxes! I wish you the best of luck. I've never heard of orange mint, sounds tasty!
I had a delicious chocolate mint plant I used to make tea from, and it came out alright.
I'm not an expert (yet!), but here are some random ideas:
You might look at the soil conditions. Overly acidic or alkaline soil will affects the flavor of plants.
Last year we grew some tomatoes in STRONG mushroom fertilizer. They came out tasting like peppers. Biting into thai peppers grown in that soil tasted like a mouthful of battery acid. We had some great times handing those little devils to unsuspecting friends.
As you mentioned, give the plant a bit longer to grow. My guess would be subtle flavors might take a bit longer to develop.
Also... growing mint with chives might change the flavor a bit.
I'd love to hear from someone more knowledgeable!
On a related note, thanks GeekgirlUnveiled for sharing the great drying method.
Best method. To improve flavor and color retention, use paper lunch sacks, put the greens inside and loosely tie closed around the stems, then hang in a cool, dry place from the stems. The greens should have plenty of room (don't flatten the bag on them.) It takes a touch longer this way, but the herb quality is much better and definitely worth the extra effort.