With each new order, buyer is eligible to have 1 3-month temp license to cover their transitional period. For Small Business license owners, they will then need to submit the domain/subdomain name(s) to generate their permanent license file. Once the names have been registered, change of such name(s) will involve a fee for license file update.
Of course, if your customers have problem keeping to the same domain names, Small Business License may not be a good choice for you. You can consider Domain license one by one and each new domain license will get you 1 3-month temp license vs SMB license only gives once. Or you can consider bigger license options, developer, developer team, enterprise etc.