One other thing:-
The present prototype when in 'Auto' memory depth (which is currently the only memory depth exposed to the user and otherwise behaves similarly to the Rigol DS1000Z 'Auto' function) uses all available RAM as a history buffer. With 256MB of RAM and at 50ns/div (~23k wfm/s, 610 pts), this gives approximately 17 seconds of history buffer that is recorded in real time. In my mind, this is far more useful than any infinite or variable persistence feature, and as far as I can tell, only Siglent expose this in normal use - which led to Dave complaining about it as it was turned on by default. As far as I can see, there is no reason not to enable this function by default, as it is just a case of walking through memory pointers. If the user selects a larger memory size, then the instrument will have less record time, but should always have the amount of memory available that the user requests.
Most people know this function as segmented memory. The only difference is it's a continuously active segmented memory function, which adapts to current settings to make the most use of the memory available. It avoids that headache of pressing the 'STOP' button and missing the trigger by a few milliseconds.
This is one time the user might want to turn down the waveform rate as e.g. reducing the update rate to 1k wfm/s would increase the memory time to over 6 minutes. Giving the user that trade off is valuable (this is pretty much always found on scopes with segmented memory). Depending on the future platform choice, I expect a later version of the scope to support at least 1GB of RAM which would give around 900 Mpts of usable waveform memory. So at 23k wfm/s, instrument could record ~1 minute of waveform history and select any one of those timestamped frames or analyse any single given capture.