I honestly think that very, very few webmasters are earning more than $50 per day from affiliate marketing (that's $1,500 per month). Some months I make it to that level, and some months I don't. Some merchants and some networks don't pay me every month (Amazon is the big example); others deposit into my checking account every single month.
It's hard to say "how long it took" because I usually lump all "revenue" together, whether it is CPM-based advertising, Pay-Per-Click advertising or search panels, or affiliate earnings. I know I created my first web site in 1996, and I know that two years later I was earning $10,000 per month in combined advertising/PPC/affiliate revenue, but most of that was probably regular CPM advertising. Then I sold off my best "cash cow" web site in 1999, and most of that revenue went to the buyer of that site. I also sold several other web sites in 1999 and 2000, with more of my revenue passing to those buyers.
When I am busy with consulting work (as I am right now, serving as interim affiliate manager for QuoteProducts.com), my web sites generally lose traction and revenue. When I have free time, I enhance some sites and create other new sites, and the revenue ticks upward again.
Each of my active web sites has its own cycle now. One site focuses on teachers, and it will certainly generate $1,000 in affiliate earnings this month and probably again in September (it's back-to-school season). Some other sites are heavily retail/gift oriented, and thus they tend to earn more revenue in Oct-Nov-Dec than in the other 9 months combined.
Some of my revenue comes in bizarre spurts. Often, these spurts are caused by search engines: suddenly Google decides that it really likes one of my sites, and for a week or three I am seeing revenue from a bunch of motorcycle helmets or skin creams or iPod accessories. Then Google updates its index and that revenue slows to a trickle.
