On Fri, Nov 22 2024, Eshel Yaron wrote:

> Done, in 097b685aa1c.
>
> Tomasz, setting this new option flyspell-delay-use-timer to non-nil
> (after building Emacs from the master branch, or applying these changes
> to your copy of flyspell.el) should hopefully resolve the extended delay
> you've been seeing.

Thank you Eshel and Eli for quick resolution of this issue!

Setting flyspell-delay-use-timer to non-nil indeed helps. The delay set with completion-preview-idle-delay option is not extended when flyspell-mode is active as well.

Kind wishes,
Tomasz Hołubowicz