We can blame EU directives for the degrading of sealants and paints ... their rules on VOC ( volatile organic compounds ) meant that proper paints could no longer be manufactured, I guess same with sealants - the modern ones seem to inferior to older ones.. same with no brainer plan about adding ethanol to petrol which corrodes the system and attracts water, causing many problems that should not exist, and the EU seems to accept the fact that rainforest is chopped down to provide land for growing sugar cane and maize to produce the ethanol... the lunatics have truly taken over the asylum....
I used to creosote wooden sheds and fences, which lasted ages, not allowed to use creosote anymore, instead have to pay or more expensive inferior products that need re-applying every year or so..