Can we schedule weekly or monthly imports using Import Tool?

Yes you can schedule weekly or monthly imports using Import Tool. You can use Windows built in task scheduler (Control Panel -> Scheduled Tasks) together with Import Tool command line version (ImportToolCmd.exe; you can find it in the same directory where Import Tool was installed to).

You need to specify some parameters, like project name you want to run, log file name, etc. Execute ImportToolCmd.exe from command prompt to see all available options.

You can create a simple batch file that will execute ImportToolCmd.exe with options, this would simplify whole process (this way you can embed all parameters in the batch file).

Please note that the scheduled task needs to be configured to run as a specific CRM user, who has all required CRM permissions.