Radio Link Timeout is somehow related with drop call rate. In some literal example, we may experience long duration of bad quality call but still the call doesn’t drop also in reverse we can also experience not so bad quality calls but suddenly it drops. RLT may be related with this scenario(but still consider some other factors and parameters).
The value decremented by 2 every non decoded SACCH (corresponds to poor c/i) and incremented by 1 every decoded SACCH(good c/i). When this value reaches zero, drop call may be experienced. Thus setting the RLT too high means prolonging the calls eventhough bad quality is experienced.