Prepared Statement Question

We have a question regarding prepared statements. The following code is located in src/backend/tcop/postgres.c:   /*
Getthe parameter format codes */   numPFormats = pq_getmsgint(input_message, 2);   if (numPFormats > 0)   {       int
i;      pformats = (int16 *) palloc(numPFormats * sizeof(int16));       for (i = 0; i < numPFormats; i++)
pformats[i]= pq_getmsgint(input_message, 2);   } 

There is similar code for Parameter Lists (ParamListInfo) and Result Format Codes (rformats). Unless we're missing
something,a prepared statement would probably never change once prepared.  
Would there be any issue or benefit moving the allocation of these buffers to the PreparedStatement structure so they
staywith the prepared statement throughout its life? There is probably the question of named versus unnamed prepared
statements,but is there anything else that we might be missing? 
Along these lines, would it also be possible to keep an Executor State and Expression Context with the statement and
justreset key parts of them, rather than rebuilding them from scratch each time a prepared statement is executed? 
Thanks
David