Changing the lease time shouldn’t affect anything except how often your computer requests a renewal. A computer will start to ask for a renewed lease from the DHCP service after half of the lease time has expired. The DHCP service will issue the system a new lease on the same IP address when it receives that request. How often this happens should not have any effect on your use of that computer. The lease time only counts while the computer is connected to the network, once it disconnects, the lease is terminated. Most DHCP services will give a computer the same IP that it had last time it connected if it is available, but not all. You can’t simulate a static address by playing with lease times.