So far when you buy new equipment etc. using 179 I think, you can write off in that year, was up to $250K, but I think that its less now. Bottom line is that you write if off in the year that you bought it. If you buy more than the max 179 write off, then you depreciate that amount over how ever years the IRS says that you can (more or less the life of the item). For more depreciation you can buy another business/wash and if its a S corp/LLC or sole P then you can take it from all of your income.
Now here is a problem that many forget. Lets say you bought something/business for $500K, you depreciate it over 7 years, and then someone comes along and offers you $750K as that is what things are worth at that time. You now have what is called recapture, in which the IRS requires you to return the deprecation as it appears that it didn't really become worthless.
If you sell this on a contract getting say $200K down, you may find that it all and maybe more needs to go back to the IRS in the year of the sale. Yes, you can do a 1035, (I think it is) exchange and postpone the tax on that sale, but of course you open up new cans of worms. You will pay the taxes eventually, just hope for inflation (another two edged sword) where you pay with cheaper dollars.
Different CPAs have different thoughts as to what is the smart thing to do, but you yourself need to understand the ends and outs of the tax issues, because you are the one that does the paying.