Not enough date/time custom fields

[Ashley]

I currently are using custom_21 to custom_24 for various date/time field requirements (for 4 environments).  However, I now need two more date only fields for Sign off date and post sign off date.  There are only 5 custom date/time fields.  So I have one spare custom date field that I can use, but what about one more.  There aren't enough custom_date fields.  If I use one of the other date/time fields 21-24 then they will obviously over write previous data for a record.

Please advise what I could do to achieve what I need.

Thanks