Once you've constructed your "lead book", you need to be careful about the timeliness of your data. Consider this back-of-the-envelope calculation: people in tech switch jobs every 18-24 months, meaning at best 1/24th of your data expires every month. If your data provider refreshes their database every 6 months, then you run the risk of having 6/24 (1/4) of your contacts being stale, increasing the likelihood of bouncing. Once you've identified a list of high-value leads to contact, it can be worth doing a secondary scrape of LinkedIn to confirm they're still at the company.