Yes, gaming rig. I count on 5-year use (OC i7 4790k) and 1440p + 1-2 time upgrade on GPU, and alredy have both kit.
In general I'd really recommend against mixing RAM anyways so just go for a 2x8GB kit, which will give you room for expansion to 32GB in the future since most 1150 mobos take up to 32GB of RAM.
It'll be a looong while before you need more than 16GB. If you can find identical sticks then upgrade to 16GB total. If not and you want more RAM, sell the old kit and buy a 16GB one.
16GB, 24GB or 32GB?
What is the usage of your PC? For mainly gaming, I do not think you will ever need more than 16GB until your current 1150 rig is completely broken.
Yes, gaming rig. I count on 5-year use (OC i7 4790k) and 1440p + 1-2 time upgrade on GPU, and alredy have both kit.
In general I'd really recommend against mixing RAM anyways so just go for a 2x8GB kit, which will give you room for expansion to 32GB in the future since most 1150 mobos take up to 32GB of RAM.