I feel you ludzik!
My philosophy is "buy now or forever hold your peace."
Being the case, I always have a large enough reserve LEGO fund to purchase whatever I want, whenever I find a deal.
For example, In January I bought Tower of Orthanc, Medieval Market Village, 6 Castle Forest Ambushes, the ice cream truck and castle set from the Lego movie, the Grand Emporium, and quite a few other sets actually.
But I didn't plan on buying any of these.
-Grand Emporium is getting harder to find, so when I saw it on Walmart.com for its MSRP price of $149.99, I didn't care to pull the trigger.
-Tower of Orthanc came up in "good condition" on Amazon Warehouse Deals (AWD) for $162.xx. I couldn't pass that up.
-Medival Market Village came up in "repackaged good" condition on AWD for $121.xx. That set is hard to find at that price.
-Walmart.com had dropped the price one week for the Forest Ambush for $8.75. I'm a huge fan of both factions, so I bought 6.
-I was able to get the Lego movie sets from TRU for $19.99 respectively during a $20 off $75 sale.
That's a lot of money! Now, i'm not a millionare so I can't afford this type of buying consistently. This pas Super Bowl Sunday, I had 26 different LEGO auctions end on Ebay of various sets and individual pieces, etc. The total I received (not counting shipping) was $628.xx
Once this fund starts getting low, I will list more LEGO and rinse, repeat. This way, I can keep on buying things as I want them, and reselling the sets, individuals I don't really want.
BTW, in Lamanda's selling out thread I have already accumulated a tab over $100.xx