Primes

Does the new phone come with a new discount on your plan? If not, just buy the same model from a 3rd party retailer. If so, Fizz only supports one discount at a time for your plan. With the exception of the rebates you get from your Fizz points rewards.

See section 2 here: https://fizz.ca/en/faq/what-discovery-discount-and-how-does-it-work#2

According to the Fizz FAQ, you should be able to keep your discount if the new phone does not have a plan discount:

If the new phone you’re buying is not associated with a Phone discount, you keep your current Phone discount on your plan until the end of its 24 months.

If that new phone is associated with a Phone discount, that new discount will replace your current discount on your plan. Say for example there are 3 months left to your 10% Phone discount for your plan. You buy a new phone with a 15% Phone discount for your plan. That new 15% discount will put an end to the 10% one. You’ll start a new 24-month period with a Phone discount of 15% for your plan.

Source: https://fizz.ca/en/faq/how-does-phone-discount-plan-work (FAQ #4)

@ShamanicArt said:
Or I'll just wait for nine months before I buy another phone through Fizz and hope that my present phone is going to last.

There's a good chance Fizz may have some good phone (and plan) deals around Black Friday or Boxing Day. At least that's what I'm hoping for myself!

@ShamanicArt said:
I currently have a 50% discount on my phone, and the new phone would have a $5 discount monthly. I would be shooting myself in the foot to buy a new phone. Maybe this should be modified to: if you have a discount, you keep the highest discount. I'd be cool with that.

It's a real good suggestion. May be it is already possible if you speak with someone of «Service à la clientèle» via the support. It's a chatt which you can reach someone of this service after few steps (robot first, agent de premier niveau after, and someone of the service à la clientèle at the end.