Apple will provide after sales support for many years. If I were to buy a laptop today, I would seek a factory refurbished Apple which offers price, performance and support.
If you want Windows, then try to find a company which you can witness providing good support for their older laptops. This is the only protection you will have after purchase is made.
You have to think a turn ahead, because when it comes time to sell your aged laptop, the potential buyers will want it to last them a year or two. Even if reliability doesn't bother you, for decent resale value, you will almost certainly need to replace the battery. To gauge whether or not replacements will be available, check the vendor provides reasonably-priced batteries for their older laptops before buying a new laptop.
The biggest problem is that Windows is customised by the vendor for the rare hardware found in their laptop. You will have to wait a generation or two before you can expect off the shelf Windows to run 100% on the same machine - this hindres Windows upgrades. I had a Compaq that shipped with a customised version of Win95B. Win98 and Win98SE both refused to work on that machine because of missing driver support and Compaq provided no updates. WinME worked fine. So the upgrade path was Win95B -> WinME.
Vendors do not normally provide drivers for any OS other than the one your laptop shipped with.