Hi Vishwa,
As of now I never come across restriction in 250 + control parameters and info parameters. One of the project, when we thought about control parameters to load then we moved most of the key fields to we crossed more than 300 control parameters, however other than performance. You have to think about SAP EM Web UI performance on control parameters if you client view data through WebUI too.
SAP EM WebUI not strong enough to hold more than 50 columns to retrieve data and you get round symbol and takes more time to retrieve data. If you don't use SAP EM WebUI then well enough.
As you know, control and info parameters are different data records those are in data container and used Parameter name and value string and index method. So, it will impact the performance even you have a robust system in place to address. If data volume increases over the period, then each FU loading time takes extra bit time and updating 250+ fields consumes more and more memory, CPU and disk space.
Best approaches:
1. You can move most of key fields to System parameter if those are holding multiple values in it.
2. Check with client what are the important fields require for business to load data (most of clients not using 70% data which they requested initially in the project)
Regards
GGOPII