99 pages is a lot of trades. I usually do 25 to 50 pages. Before you say WHAT!, first consider that you don't know what is in demand so you need to cover your bases. Second, do the math. With 5 goods per age, trade each up or down for 5 goods of "the other age", and 10 trades of 20:10 or 10:20. That works out to 250 trades (5x5x10) and at 10 per page is 25 pages. Do this for two ages and you have 50 pages of trades.
I switch to mobile to post trades because it is at least 10x more responsive than on PC browser.
I do wish they would reconsider grouping the same trades by player and using a quantity column (Player A, Offers x amount of good B for y amount of good C, X trades available). This would prevent buyers from having to wade through multiple of the same trade they are not interested in while also allowing for the posting of a quantity of the same trade (instead sending 500 trades to the server, it would only be 50; ie., a 10x reduction in network traffic).