Hi ,
Seamless data acquisition is only possible in a single acquisition. If the data that you capture is split over multiple acquisitions then there will be gaps between them. For that reason, your maximum length of seamless recording is limited by your maximum record length and minimum required sample rate. In the case of your DPO4104, the RL is 10M points. If you only needed a sample rate of 10KS/s, then you could record up to 1000s in one acquisition. If you needed to sample faster than that, you would have to sacrifice on the length of the acquisition.
There is one other limitation here, which is the 400s/div maximum horizontal scale on the DPO4104. This means that even if you continue to lower your sample rate, you will only ever get a maximum of 4000s in a single acquisition.
So the questions become how long do you need to acquire data for, and how frequently do you need to sample?