I also ordered the CEM40 mount a few days ago and expect delivery within a few days from now.
I'm expecting that with this mount doing unguided photography at f=400mm should be possible up to 90 to 120 seconds. I succeeded doing 120 seconds exposures at 2000mm (yes, three zeros) with my LX85 and I consider this a quite cheaper mount compared to the CEM40 (yet to be proven by experiment). This was only possible with an extremely careful polar alignment which I achieved through drift alignment (my personal favorite) since the LX85 is per default not shipped with a polar scope.
As bobzeq25 said: get into auto guiding. What I said above was for the sole purpose of getting to know my mount. Here's a list why you won't be able to shoot for longer exposures without auto guiding:
1. Lack of perfect polar alignment. If you want to get the accuracy from above, drift alignment might take an hour if done with only a reticle eyepiece. If you're using software, your just one step away from auto guiding (so this doesn't count).
2. Periodic worm error. Every! worm drive has periodic error. Depending on the money you spend, this is more or less. Nevertheless, it's there and especially the longer focal length you are using the more you will notice it. Typically a full worm revolution is about 7 to 10 minutes. So the gear has sufficient time to ruin your image. Periodic error correction will help a bit but won't eliminate everything. It mainly "helps" the auto guider as it doesn't need to correct that much.
I don't know if I'll give it a shot to see how far I can drive the CEM40 without auto guiding. Maybe only for testing the mounts overall quality but not for daily use.
The more interesting questions with the new mount would be: how accurate will the iPolar be? How well is the drive responding to guiding commands? Is the dec backlash within a good range or excessive (my current problem with the LX85)? How about max payload? Does it handle 50%, 80%, 100% max payload well?