Hello,
subscribing to 1000 points and getting updates for each item once a minute is definitely something that should work. Different applications have different needs, but I can say that in general case, recommended approach is simply to call SubscribeMultipleItems once, with all 1000 items.
If you get an exception, then something is wrong. But there are many different possible causes, such as:
a bug in our component
a bug in your program
a problem reported by the OPC server
I need to know all available details of the exception and symptoms of the problem, in order to tell which of the above is the case, and how to proceed further. Is that an en exception thrown by a method call? Or does it happen asynchronously? What is the message text? Can I see the relevant pieces of your program? Etc.
To the question about number of points vs. number of updates: After the subscriptions are made, the load on the system is created mainly by the change notifications, and as such, it will be comparable in the two examples you gave. This is true if all the points actually DO change - but if they truly change let's say each 5 seconds, then asking for 1 second notifications may require more work from the OPC server (and the communication to the target system), but not on the OPC client side, because the client won't get to see the values that don't change. But the whole question is kind of distracting, because the subscruption rate should be dictated by the application needs and nothing else, so you really have not much free option here.
