A few thoughts on your application.....
First up, you mention that you are not running a control strategy.
If this is going to be the case the whole time you are needing to log these temperatures, then you might consider turning off the control engine on the controller.... This will give the controller more time slices (CPU cycles) to address the TCP/UDP stack.
Check out page 141 of form 1704, the PAC Manager Users Guide, on how to do this.
(While you are there, are you using any digital I/O modules? If not, also consider turning off the digital scanner as well. Just add the two values together and put that into the scanner flag).
We had to do this on a customers job late last year and it made a measurable improvement in throughput. (Just how much will depend on a lot of factors, so its impossible to give hard numbers).
Next up, if you can, get the controller and the laptop on their own network.
The whole TCP/IP network traffic issue needs to be removed from the controller.... The very nature of TCP/IP means that the controller has to check each packet and see if its addressed to it.
Don't be tempted to simply use the second port on the controller, this will not remove the CPU load from the controller.
You will need to use a single cable between the controller and the laptop and put a fixed IP address in the laptop that matches the one in the controller (ask Google how to do this if you are not sure, Im told it knows stuff like this )
Lastly, at the rate you are talking about, I have to raise the question of the module freshness.
If you look at the data sheets on our modules, they all have a 'freshness' value.
For example, the SNAP-AIRTD, a pretty typical module that uses 100-Ohm Platinum RTD probes to measure temperature, has a 'Data Freshness' rate of 100ms.
You can read it more often than that, but you will simply be reading the same value over and over.
(And keep in mind, like Mary said in the post above, this module freshness value does not take into account any thermal inertia that the probe itself might have).
Lets know how you get on. Pretty interesting application.