You can just buy the current version of the software, which is the one-time payment you describe. This version shouldn't stop working, although future SQL Server versions will surely have features that it can't cope with.
You may wish to purchase a support contract as well, which will entitle you to new versions of SQL Compare at a lower cost than purchasing each upgraded version.
Answers
You may wish to purchase a support contract as well, which will entitle you to new versions of SQL Compare at a lower cost than purchasing each upgraded version.
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