You adjust the schedule as required and don't do it for projects with tight deadlines.
The truth is if you don't ensure your developers career development is baked into your schedules then you get a combination of high turnover, unmotivated engineers, and engineers who learn on the clock "in secret" by making decisions that are best for them rather than best for the company.
All of these cause far more problems and are harder to account for than being upfront in the first place.
> and engineers who learn on the clock "in secret" by making decisions that are best for them rather than best for the company
Yes, and possibly not even consciously. Without that constant reminder of the pitfalls and learning curve of new technology, it's easy to convince yourself it's all upsides, or at the least undervalue the downsides.
The truth is if you don't ensure your developers career development is baked into your schedules then you get a combination of high turnover, unmotivated engineers, and engineers who learn on the clock "in secret" by making decisions that are best for them rather than best for the company.
All of these cause far more problems and are harder to account for than being upfront in the first place.