The advert is for an "upgrade" and appears to be a permanent fixture. I don't think it's possible to turn it off.

Aggressive marketing

Yes, the one in the bottom right is just there. I ignore it, but was able to turn off all the others in Options. I don't think it's really aggressive unless it's flashing at me and I have to click through more than one thing to get out of it. Or if they start sending me multiple emails every day. A small button just sitting there is just there.

Well I intensely dislike things like that.
When one's been there for months it's obvious that if I wanted to take advantage of it I would have done already !!
So I can consider it "aggressive"

I do a 'GRRR..." at my banking website! EVERY time I go there, they ask me if I want to sign up for mobile banking and my choices are yes, ask me later and decline. Wouldn't you think if I select decline, it means NO!

I agree with you, Mad.
I appreciate that they may want to get some of their development money back, but when they do things like send emails all the time with "offers" or flash nags in your face, I have no confidence that paying for the program would put an end to the various types of nags.

One of the reasons I "donated" to Irfanview many years ago was that it "didn't" have nagware.

Nagware only makes me look elsewhere.

And if they call something a "free version" it shouldn't have nags.

I also donated to Irfanview for the same reason some time ago. Great free software, but no nags. Many years ago I also donated to CCleaner for the same reason. But Piriform has also gone to these Pro versions which really don't provide me any value. But I can live with a quiet small box in the corner that doesn't pop up or flash or send me emails.