You have 30 days grace period after the due renewal date. If you let your maintenance lapse then you will no longer be eligible to receive new releases of CAD Exchanger.
Your access to your customer corner and other online resources (such as Knowledge base, FAQ, forum) and our support team may be limited or switched off.
You will still be able to rebuild your application with CAD Exchanger SDK (using any version you received during maintenance). Your application will still continue to run and thus your end-users will not be affected.
Although you may still submit a bug report, it will likely be registered with a lower priority, and you won't be able to benefit from the fix anyway (unless you resume your maintenance).
Renewing your maintenance is more cost-effective from financial standpoint and more secure from a business continuity standpoint. Should your end-users report some particular issue (a CAD file in a recent file format version, new OS, a specific bug) and you don't have active maintenance, you won't be able to take advantage of the enhancement in CAD Exchanger unless you resume your maintenance.
Should you decide to resume your maintenance you will need to pay a welcome-back fee, which is 90% of a then current new license fee.