At what point is it too late to build Rod of Ages?

I play a lot of AP champs, and most of them scale well with RoA. But sometimes I get so bossed in lane either by a camping jungler or because I just get straight out played. Sometimes it gets to like 20 minuets and I still haven't completed it. So I'm wondering what is the average point in the game where RoA is no longer worth completing?

Solution 1:

RoA:

Your champion gains 18 health, 20 mana, and 2 ability power every minute. Bonuses cap at +180 Health, +200 Mana, and +20 Ability Power. Unique: Upon leveling up, restores 250 health and 200 mana over 8 seconds.

If you check, you need 10min to get the RoA with his full power.

Take this in consideration in EVERY single game, some times a game will last for 1h (60min) others only 25min or even 20min.

• RoA is a item that you can get at early and mid game.
• You can get RoA at 40min if you see the game flow is slow and will last for at least more 15min

Conclusion: Take it with 15min or more for the end of the match (You can estimate it after some time of game) Usually 25min is the maximum available, so the game will end with 40min.