Group Therapy: Reinvesting

Whenever we have profit, a piece of it gets reinvested back in to the AH. But what if you'd have 10K+ , 100K+ or 200K+ (!)? Is it possible to keep reinvesting? If so, how much, in what, and even why?
Personally, i invest 50% of my profit. with other words, if i earn 5G profit, i would use 2.5G for the AH and keep 2.5G. Yes, this makes progress slower, but then atleast I still have some back up money if something goes wrong. Ofcourse no two minds are alike and some would even shoot me for doing it this way. I know i'm not the all powerfull Guru, there are others out there.... well, for once they are here. And they are sharing their thoughts....

Zekta:I keep a comfortable level of cash (currently 4k).
my balance will be always on 5-6k level. So whenever opportunity hits, or I need for spending, there will be 2k cash for me. (if I need more, e.g. for a given gear, I'll save them up up front)
I normally invested in Ore, Ethereal, Pets, Leather, Gem. Whenever they're cheap or will raise for patch later. Sweet Deals are much harder to find lately, so I called for COD for Nether Cloth, Books, Herbs (For ink, I had 1-2 month ink supply now :( ). Am looking into noble card for that, but seems not so profitable in my server. I am still looking for other business to do (or to burn those extras ) peeking on JMTC's forum now.

Grodus: I play on a heavily populated horde server. Many of the markets are difficult to break into because of this, as there are some players who post auctions almost constantly, but I've learned to reinvest very strategically. In a given week, I tend to spend 2-3k gold to make back around 5-6k gold. It's not a huge amount of my overall gold as I'm usually sitting at around 20k, but it's a good number for anyone who wants results with less risk.
It's very important when reinvesting to know when to buy and know what to sell. I've found that the two best times for stocking up (and this will vary from server to server,) are Monday night before server maintainence, and Friday night. A lot of farmers will post their items Friday night to get ready for the Saturday rush. There's gold to be made there.
As for what to reinvest in, do some research on the items people need to have for raiding. Flasks and gems are great to buy on slower days and post them again on heavy raiding days. Even better if you have an alchemist. If you know of items that are useful for raiding, do some research. Even if someone has cornered one of these markets you can still make a profit by supplying the supplier.

Three seperate views gives a nice depth to the post don't you think?
Thank you Grodus and Zekta for doing this with me!

And remember A fortune starts with one copper!