Ndiddy,
Yes, it is within 13 weeks from the last day of your old policy.
It is important to renew your cover before going away as it will mean your health cover will lapse.
This means that you will be treated as a brand new customer again and would have to re-serve all new customer waiting times.
For example, 5 years waiting for pre-existing conditions and just accidents and injuries covered for the first 6 months.
The bottom line is 'don't wait until you come back' if you want to avoid lapsing your health insurance.
Travel insurance is a totally separate type of policy and is not a replacement for health insurance.
Snowyb