When to monitor a sales using a lead or potential

When to monitor a sales using a lead or potential

hello

We currently import leads from their website into zoho as Leads.

For those companies that we make a sale to we convert them to potentials, accounts and contacts.

my problem is this, if we do not make a sale to one of the leads, then we wish to try to make a sale to that company the following year as we deal with yearly contracts.

If we have converted that lead to a potential then my understanding is that it is deleted as a lead. If if therefore we do not make the sale awe have that persons details as a potential that was not won. This situation makes it very difficult when we are looking to do mass e-mailing in future years. 

So my question is this, can we convert a lead to a potential and leave the lead still there, or can we revert the potential back to lead for future marketing purposes?

At present we handle all the presales activity as a lead and only convert them to a potential when we know that we can sale.  In our industry having made to sale we then have to ensure that the contract goes live before we can receive payment, so there is still quite a lot to do.

Any comments welcome.

Regards

Steve

I have dictated this using dragon NaturallySpeaking so apologies in advance if there are any errors.