It could be an issue with particular OPC Server and now with datasocket.
I would like to recommend to check if you have same issue with NI Server, for example, connect to
opc://localhost/National Instruments.NIOPCServers.V5/Simulation Examples.Functions.Sine1
I've used DS in such form many times and haven't seen such issues so far (not from LabVIEW side).
In given example you will collect your data in for loop (on indexed output), but if you run it 30 min only with once per second - it is only 1800 DBL readings, is it nothing critical, should not lead to freezing anyway.