Or are you saying one must immediately buy the market, always? That seems simplistic in the extreme.
One should always be in line with their asset allocation, yes.
Spuriously changing because of a sudden windfall seems like a good way to make a mistake.
When you get a 'windfall' payment, despite a long-term AA target, there may be different strategies to phase the allocation of the cash into that portfolio - is that short-term market timing?
This is a different question. You should be investing with regards to your AA, but dollar cost averaging is perfectly fine, in fact often recommended.
The way the question is posed in this thread, it's not "how do I phase in a windfall to my AA." We'd need much more information for that.
With the way it's phrased you'll get junk answers like "GOLD NEVER GOES DOWN" or "I <<<<333 REAL ESTATE" or "PENNY STOCK XYZ IS AMAZING" .. even if answered intelligently, "I think you should buy real estate because of reasons X, Y, and Z," it won't necessarily be good advice for you
Thus my original advice: It seems to me you need to sit down and figure out what your AA should be. Then execute.
If you'd like some help with that, no problem, I'm sure lots would be willing to chime in. But to just say that you want to throw a big chunk of cash at some random investment not in line with your long term goals, risk levels, interests, etc. seems... unwise. :)