You must assertively build your data set year after year with all potentially relevant sales or commerce contacts and ensure your follow-ups are well-timed and organized, so you can contact just the right people at just the right times.
If you have organized your contact management system properly, then having huge amounts of data will not be clutter; instead, it will be power at your fingertips.
The key is to have as much data as possible about each lead stored in the right fields, and to make sure every lead has a calendar date for when they are to be reviewed or contacted again. If you have determined them to be a critical lead and a likely deal, then the calendar date is tomorrow; if you decide the lead is unlikely to ever close, then you can make it five years from now or delete it. In each case, your data set will be clean and meet a logical, simple business flow.
