Reports -> (Bottom left corner) -> Admin Utilities -> Advanced Lead Management Tools
Move Leads - based on Date of Entry or last Modfication. This would allow you to segregate the leads by date. You could then deactivate the new list to avoid dialing those leads.
Update Lead Statuses - based on Date of Entry or last Modfication. This would allow you to change the status of old leads to a non-dialable status.
Delete Leads - based on Date of Entry or last Modfication. This would obviously match your request, but would also block some reporting (which could be awkward moving forward).
Alternately, you could create a filter that omits leads based on either entry date or modification date. The creation of a filter would mean you would not need to alter the leads themselves at all and *could* alter your strategy in the future and include some or all of those leads merely by altering the filter. The filter also is an instant change which does not require constant supervision. But beware: If you have a huge list table the filter can be costly from a CPU standpoint.
But when you download and re-upload leads you generally tend to disconnect the leads from prior log entries unless you only Modify the leads during the upload script to alter their statuses (which can also be done: The command line loading tool has an option for modify if I recall correctly).
Moving this thread to the Support board as this is obviously not a "General Discussion".
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