[bbwbsb]

I prefer: do the thing when doing so reduces the expected cost of (time-discounted) future outcomes by more than the expected utility of the next best thing you can do now.

The problem with DRY occurs when it contravenes this principal - when deduplication is too expensive and/or unlikely to decrease the cost of future mutations enough to be worth it.

The proposed problem isn't a binary - that you should or shouldn't make the assumption yet - but rather that the assumption has a cost based on what you believe is likely to occur in the future and the value produced by making the assumption now needs to outweigh the cost.