Help required for TTL.

[Salman Ahmed Hashmi.]

Good day,

Can anybody suggest,
While defining a feasible ttl value for a domain,

1)Is there any relation b/w the available bandwidth (i.e link capacity
)to nslookups ?....
And,
2)How can an adminstrator know which domain needs a faster update and
which domain is comparatively dormant for setting TTL value in the soa
records.

Regards