There are two reasons, the first is there. The second reason is my job. I'm employed as a support engineer for company-use of Firefox/Thunderbird for 11-12 year

There are two reasons, the first is there. The second reason is my job. I'm employed as a support engineer for company-use of Firefox/Thunderbird for 11-12 years, and the knowledge and trust are based on my addon development experience. So, I think I already monetized from addons and donation looks like a double-dealing for me now. (So after I retired I may accept donation, if Firefox and my addons still alive.) Anyway, I just say thanks to all!