Will pseudobridge cause issues in this configuration?

Hi,
I had posted a design question earlier and purchased the suggested product. I have the rb433 and backhaul to tower up and going and everything is working ok.
To get it to work, I have ether1, 802.11a (wlan2) in station-pseudobridge, 802.11g (wlan1) in ap-bridge with all 3 interfaces in a bridge.

Once every hour, and only once every hour, a device at the default gateway location polls all of the 802.11g to Serial Terminal server devices by IP address. There will be up to 150 Locations, with up to 5 802.11g to Serial Terminal Server devices at each location. Currently it is setup as a single Class B subnet.
Heres the question(s)

  1. since the devices are only polled hourly, and there may be NO client traffic for that hour at a Location(s), will pseudobridge cause an issue with perhaps the MAC NAT or the arp table or cache clearing out?
  2. Should I consider breaking this into subnets at each location? or maybe create VLANs, 1 for clients per ssid, 1 for Serial to Terminal devices, etc?

thanks
ds
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Anyone? will pseudobridge arp table timeout and not let me connect to devices behind the station side?
can i create a static arp table?