Deed of variation and two-year time limit

[TedSwippet]

Following on from this post ...

One of the inheritors might need to prepare a deed of variation. My understanding is that this deed needs to be created within two years of the death of the deceased. However, because the number of other inheritors is still unknown (deceased was intestate), the amount this inheritor will receive is also unknown. The range is potentially very wide, from perhaps £300k down to £60k or less. At the upper end, a deed of variation could be advisable; at the lower end, no need.

Is there any disadvantage to creating a deed of variation where it might be unnecessary? Can one be entirely cancelled if the amount actually received is below the need for one, so that any excess money received can be simply given away as desired without problems? Or, are there good reasons for creating one now anyway, even though it might not seem to be needed at present (for example, another surprise future inheritance pushes this person solidly into inheritance tax territory where they previously were not)?

And for extra credit -- although this is not my problem -- I wonder about the other potential inheritors in this estate? Some of them will not even know that they are in line for a bequest until after this two-year variation window has closed. Are they simply barred from creating a deed of variation, even though they may well need to themselves?

Thanks for any insights. Inheritance tax is a complete nightmare. Unpicking it doesn't require an account or solicitor, it requires a philosopher.