Hang on, don't dive in too deep yet.
Rubber & sulphur are characteristics that can be imparted by sherry wood.
Whether they are positive or negative features in a whisky depends on (a) how concentrated or pronounced they are, and (b) whether you find their presence harsh & out of balance or whether they gel nicely with the other flavours on offer.
Some of the best ex-sherry casks I've ever tasted had a touch of sulphur and rubber, but these two flavours/aromas added enormously to the richness and complexity of the whisky, and I definitely thought they were positive features. (e.g. SMWS Longmorn 36yo; private bottling of Glenfarclas 30yo; Macallan 1954; Macallan ESC IV; SMWS Glenfarclas 38yo).
You'll notice that each of the whiskies I just listed are quite old, and so yes, the chance of finding sulphur & rubber increases with older whiskies, but this obviously because the spirit is spending more time in the oak from which these characteristics originate.
Having said all that, there is the well known cask of OMC Talisker (or Tactical) that was too sulphery in a very unpleasant sense.
My only point is to simply counter Lawrence somewhat and point out that not all sulphur or rubber is bad.