The main drive is the interest and what keeps you happy.
There is no need to be a "millionaire" or be a "corporate big gun" to be a happy watch collector. There will be watches that are within your means and will make you smile and make you want to own it. But to answer your questions:
1) above 40
2) this depends - my collection ranges from USD1,000 to USD45,000. I would not like to look at the averages - there are watches that warrant the high end of the range.
3) more than 100 (quite a few are pocketwatches) - I have been at it for some years now.
4) again it would'nt be quite as fun if collecting means looking at it this way. But it should be kept within what you can afford and what you are comfortable with.
5) there are times I go without a new addition for months and there are times when I acquire three or four pieces a month
6) like above - it is difficult to quantify - but for this year - I took in 11 new pieces
7) honestly, I do not know - nor do I want to find out
8) "Top Brands" are subjective - but I have the usual - for watches, PP, Breguet, AP, Lange, FPJ, Chopard, JLC,...; for pocketwatches, American watches such as Hamilton, Ball, Gruen, Waltham, Elgin, Illinois, non-american, PP, VC, Zenith, Longines ..
As you can see I collect rather haphazardly but as I said as long as it is a watch that makes me smile and I can afford it - then. Another thing - I do not "flip" my watches as I believe when I buy it it should mean something to me. For me collecting is not about making a return or making windfall in the future. My collection probably would not even make the original "investment" and I accept that. I will probably not be able to wear (use) all my watches till the end of my days but it is alright I just love to take them out now and then to touch, wind and enjoy.