Tier - 2 General Visa renewal

[maipra]

Hi All,
Hope My email finds you all in well.
I have being living in UK since Dec 2018 and my Tier 2 visa is due for renewal on 03 Nov 2021. My Employer is enquring me on the requirements of new Cos Validity. They want me to advise them how long the next renewal is required, I knew we can apply for ILR after 5 years from the date of entry. However, need confirmation.. is it good to renew for 2 years or keep some buffer time & renew for 2 & half years..., dont want to be running short of days before eligible to apply for ILR.

Firstly; Orginal Visa Date of issue 05-11-2018 valid until 03-11-2021 (on BRP)
Date of arrival in the UK 29-11-2018. Entered 24 days after start date of Visa.
If extended for 2 years then new visa will be until 03-11-2023. But the end of qualifying period will be 04-11-2023 starting from initial issue (05-11-2018).

Secondly; When should I submit renewal application? if I apply to early, renewal will be grated from the day visa issued or will be a continuation after the expiry of old date.

Any advise or recommendation would be highly appreciated.
Many thanks in advance.

BRgds...
Praveen