I am developing an application that, when bought, can be activated using a license.

Currently I am doing offline validation which is a bit troubling to me. I am aware there is nothing to do against cracks (i.e modified binaries), however, I am thinking to trying to discourage license-key pirating. Here is my current plan:

• When the user activates the software and after offline validation is successful, it tries to call home and validate the license. If home approves of the license or if home is unreachable, or if the user is offline, the license gets approved. If home is reached and tells the license is invalid, validation fails.
• Licensed application calls home the same way every time during startup (in background). If license is revoked (i.e pirated license or generated via keygen), the license get deactivated.

This should help with piracy of licenses - An invalid license will be disabled and a valid license that was pirated can be revoked (and its legal owner supplied with new license). Pirate-users will be forced to use cracked version which are usually version specific and harder to reach.

While it generally sounds good to me, I have some concerns:

• Users tend to not like home-calling and online validation. Would that kind of validation bother you? Even though in case of offline/failure the application stays licensed?
• It is clear that the whole scheme can be thwarted by going offline/firewall/etc. I think that the bother to do one of these is great enough to discourage casual license sharing, but I am not sure.
• As it goes in general with licensing and DRM variations, I am not sure the time I spend on that kind of protection isn't better spent by improving my product.

I'd appreciate your input and thoughts.

Thanks!