Will I lose any time on my subscription if I take an offer to renew early?

No you won't.

From time to time, CCleaner may offer loyalty discounts on renewals to paying customers with an active subscription.  If you renew before your current subscription expires and keep your same license key then your subscription will be automatically extended by one or two years.

If you renew and upgrade from CCleaner Professional to CCleaner Professional Plus you will be issued with a new license key, but any time still remaining on your old CCleaner license subscription will be credited to your new license subscription within 15 working days.

For example, if you have a subscription to CCleaner Professional that expires on 1 January 2021, but on 15 November 2020 you take a a 2 year upgrade offer to CCleaner Professional Plus, when you enter your new serial key into your CCleaner product you may at first see an expiry date of 15 November 2022 - but this will automatically update itself in the next couple of weeks to 1 January 2023.

... but please contact customer support if after 15 working days you credit entitlement has not been successfully applied.

 

Note that the system that matches your old and new subscriptions may not function automatically if your two purchases are under different email addresses, or if you have renewed and upgraded more than 90 days before your old licence expires (as this would be assumed to be a deliberate extra purchase to cover more computers).  In this case, you would need to contact customer support to have your licences merged and consolidated.