The question

There are limits to how much you can use a the DRBG before you have to reseed it. But are there limits to much you must use it before reseeding? Take the following scenarios as an example.

seed     = seedFromUrandom    // Reads entropy from /dev/urandom
genStart = drbgFromSeed seed
 
(v1, gen1) = genBytes genStart // Generates random data and the next state 
                               // of the DRBG as a tuple
 
/*
    Code using the random data in v1
*/
 
(v2, gen2) = genBytes gen1 // Generates more random data and the next state
                           // of the DRBG as a tuple. Note that gen1 is 
                           // used here and not genStart.
 
/*
    Code using the random data in v2
*/

seed     = seedFromUrandom    // Reads entropy from /dev/urandom
genStart = drbgFromSeed seed
(v1, _)  = genBytes genStart // Generates random data and ignores the
                             // next instance of the DRBG.
 
/*
    Code using the random data in v1
*/
 
seed     = seedFromUrandom    // Reads entropy from /dev/urandom
genStart = drbgFromSeed seed
(v2, _)  = genBytes genStart // Generates random data and ignores the
                             // next instance of the DRBG.
 
/*
    Code using the random data in v2
*/

Background information

When I say DRBG I mean the NIST standardized number-theoretically secure random number generator. Either HMAC (SHA512), Hash (SHA512) or counter (AES 128).

Like stated in the pseudo-code entropy is read from /dev/urandom

There are limits to how much you can use a the DRBG before you have to reseed it, but are there any limits to how much you must use it before reseeding? 

Take the following scenarios as an example…

seed     = seedFromUrandom    // Reads entropy from /dev/urandom
genStart = drbgFromSeed seed
(v1, gen1) = genBytes genStart // Generates random data and the next state 
                               // of the DRBG as a tuple
/*
    Code using the random data in v1
*/
(v2, gen2) = genBytes gen1 // Generates more random data and the next state
                           // of the DRBG as a tuple. Note that gen1 is 
                           // used here and not genStart.
/*
    Code using the random data in v2
*/

seed     = seedFromUrandom    // Reads entropy from /dev/urandom
genStart = drbgFromSeed seed
(v1, _)  = genBytes genStart // Generates random data and ignores the
                             // next instance of the DRBG.
/*
    Code using the random data in v1
*/
seed     = seedFromUrandom    // Reads entropy from /dev/urandom
genStart = drbgFromSeed seed
(v2, _)  = genBytes genStart // Generates random data and ignores the
                             // next instance of the DRBG.
/*
    Code using the random data in v2
*/

Please note:

• When I say “DRBG”, I mean the NIST standardized number-theoretically secure random number generator. Either HMAC (SHA512), Hash (SHA512), or counter (AES 128).
• Like stated in the pseudo-code, entropy is read from /dev/urandom.