>what are the [u]practical [/u]consequences for following scenario?
close to none. we are still using VB6 quite a lot. "known issues" are known, and for most, a workaround is possible/known.
>Is it irresponsible to use the application (a migration to .NET / redevelopment is vital) ?
no. I have an application developed in 1996 (VB5 initally, moved shortly after to VB6) still running as of today!