How often will my plusnet value IP address change.

[#1]

I'm wanting to experiment with remote html access to a Raspberry Pi, but reading other posts, it seems that no static IP is available for Plusnet Value customers.
Does this mean I need to check with http://www.whatismyip.com  before each experiment?
Or will the IP dynamically assigned by plusnet stay the same whilst the Thompson Gateway remains switched on?
And do plusnet (or another) offer a DNS service which would keep track of  changing IP addresses as they are dynamically assigned ?
It would be of interest to hear how other plusnet customers cope with dynamically assigned IP addresses.

[#2]

Your IP address should remain the same as long as you remain connected, it'll change each time your router disconnects/reconnects.
I don't think the 582n has the ability to do dynamic DNS in the firmware.

[#3]

Thank you Chris. From what you say there should be enough stability for me to experiment.
If I want to go further, then the Paspberry Pi will need a process to periodically update my chosen DNS service provider with the IP address allocated by plusnet.

[#4]

The plusnet Technicolor TG582n does support dynmatic DNS updates. I've got it running fine with dns-o-matic. Various instructions around, but I used https://forums.opendns.com/comments.php?DiscussionID=5437&page=1