I appreciate your guesses, as the questions were sort of up in the air ones.
According to your numbers and based off my calculations, this was what I concluded:
A COB without using lenses -> +10 years of expected life, with ideal environment conditions (this is using COB each day for no less than 18 hours a day and for every day of the year).
A COB equipped with lenses -> 2~3 years of expected life, with ideal environment conditions (same operating times as described above).
I liked your dirt bike analogy but it doesn't give me a good sense of how long a lap around Daytona is. I hope this math helps others with deciding whether or not to try lenses.