Is it a big mistake to replace only a few windows at once?

We want/need to replace five windows plus a sliding patio door on the 1st floor, west side of our house in Firestone, CO. One salesman said that we could replace one at a time. One salesman said it would not help that much to do the house piecemeal. I felt that the first estimate was pretty low (local company using local installers and quoting Amerimax windows) and the second was rather high (national company, offshoot of Simonton windows). I'm still reading reviews of various brands on this web site. Of course, we only want to have to do this once....not again in 5 years or so!

Any comments, suggestions, etc. will be appreciated.

What is the question?

Both are pretty well regarded windows. In this application with somewhat comparable products, installation is critical.

Speaking personally, I would not want to install one window at a time as a company or as a homeowner. It draws the project out a bit and there is an absorbed cost every time the contract has to go to the home.

I would not advise to replace one window just to "test drive" the product or company doing the installation. Replacing several windows at a time due to budget or need is a different story.

If you lived in Chicagoland and were buying Okna, Starmark or Softlite Elements then I'd suggest doing every window in the house. Maybe some in the neighbor's house too.

Sorry, just kidding. A little sunday humor there....

Do the 5 or so that you need now. Make the right product and contract choice.
Later you will want to do the balance.