It's pretty likely that this situation could cause some problems. The obvious are:

1) Blocking - SQL Server holds exclusive locks until the transaction is terminated. If the transaction is maintained for 8 hours, so will the exclusive lock. The impact will be poor performance and probably a lot of connection timeouts.

2) Transaction log growth - SQL Server cannot truncate the log past the oldest open transaction. This means that even if you were doing periodic transaction log dumps, SQL Server would not be able to free the space in the log and the log would run out of space causing an error or file growth, depending on the log file options.

My suggestion is to add some error handling to your automated process and include some time of notification to an administrator. Email works pretty well. <s>

-Mike