When one need to transfer webhosting files to another account, he should decrease TTL (Time To Live) value in his domain nameserver records on his webhosting account.

Why decrease TTL? Because TTL value tells internet service providers how long they should cache nameserver records including IP address and nameserver name. When we change this during website transfer (we point domain to another server/IP), we need this modiffication to be quickly reflected so our repeated website visitors are not redirected to old hosting even after records are modiffied (because of their ISP caches as we told him to do)

Example: DNS Zone, DNS Zone File

I have it like this in cpanel hosting control panel
Name:  5ftLo.jpg
Views: 181
Size:  83.2 KB

So TTL appears to be general TTL of a zone file, 2 nameservers TTL and A records TTL. I have been told i need to change all 4 values from 86400 seconds (48 hours) to like 1800 seconds (30 minutes) or even 600 seconds (10 minutes) or less.

So i want to ask What is reasonable recommended minimum TTL for website transfers?