Working With TIMESTAMPS

Hello!

I think I am missing some essential idea when working with a timestamp column, maybe someone around here can give me the needed pointers on how-to...

My situation is: I want to copy data periodically from one DB to another. Both are in the same SQL instance, so there are no transaction, networking or similar issues involved. It all really comes down to identifing the new rows in source and moving them over to destination.

I added a TIMESTAMP column to my source, and I can see it count up slowly for every line inserted. On the destination side, I added a table containig just one field, type binary(8) to store the last value to which the last transfer ran.
Notice that on source side I got the counter on every row, but on destination side I got only one value, I thought it would be waste to carry over the data for every row when I really only need the latest one.

Now, what my package does is:
a) Select the last used binary(8) value into a package variable named TS of type object (works)
b) Start a dataflow, where the source is SELECT statement and the WHERE clause is TIMESTAMP > package variable TS (works)
c) Multicast the data into two recordsets
d) One recordset makes most of the columns flow through some Lookups, Derive Columns into a Destination and are written back. (works)
e) The other exit of the Multicast shall go through all lines and catch the highest TIMESTAMP that came by using an Aggregate and write it down, since that is the point I need to pick up later. (and that is the problem)

Problems are: I cannot run Aggregate max on the TIMESTAMP. Only Count is allowed.
So I need to convert the BINARY(8) into a number to be able to catch the max value. Converting between BINARY(8) and DT_I8 or similar seems not possible, or the result is wrong due to the byte ordering (MSB/LSB, most/less significant byte first)

Later on, I need to write out my new found highest value again, but here the same problem applies. How do I convert from DT_I8 back to BINARY(8)?

Having my own reference value stored as bigint instead of binary(8) does not work either: You cannot assign bigint from a select to a package variable, bigint are loaded as string (as I read in a blog, and I think they are right since I get exactly the same errors).

So...
HOW does one work in an efficient way with a TIMESTAMP column to Aggregate it to max and store out this max value?
Or do you all keep the TIMESTAMP from source appended to your rows and stored with each row in destination (Wasting eight precious bytes a row)?

Thanks for your comments!
Ralf