HTML field value size limit

Is there a limit to the amount of characters that can be in an HTML field?

We are thinking of doing some XML via HTTP and the company sending the
request would be sending us many thousands of records like the following
within one HTML field:

<xml>
<Client>
 <ClientName>Carl Johnson</ClientName>
   <requestType>b</requestType>
</Client>
<Client>
 <ClientName>Jim Tada</ClientName>
   <requestType>C</requestType>
</Client>
<Client>
 <ClientName>Buck Calabro</ClientName>
   <requestType>P</requestType>
</Client>
 . . . .
</xml>


So I am wondering first off if we are going to run into trouble if we have a
lot of <Client>'s in one form submission, and second, am I going about
transferring XML in a totally wrong fashion?

Thanks in advance,
Aaron Bartell