'Reasonable' time for disciplinary decision?

[Jellyandjam05]

I know that disciplinary decisions should be made as soon as possible and in a reasonable time but generally how long do they take?
Disciplinary was last Friday and they stated that they wanted to get it done as quickly as possible given that the investigation has been going on for 4 months already but so far we've heard nothing. Rep has tried calling today but no aswer.
Just wondering if this is normal? When does it become unreasonable?