Resin sealed caps do degrade with time and temperature cycling, the resin is not totally vapour proof, and the liquid ( and more importantly the hydrogen gas generated internally as the capacitor reforms) does diffuse through it and it slowly degrades. The only capacitors with a indefinite life are the wet solder sealed glass frit insulated tantalum types, as used in the Voyager spacecraft. Those are truly hermetic, as there is literally zero outgassing from them in a bare non sleeved case, and they will last decades in operation at 125C. Electrolyte in them is sulphuric acid, and the inside is silver plated steel or tantalum only, with a PTFE inner support structure.
The rectangular sealed capacitor referred to from Digikey I will tell you a nasty secret about some of them, they are internally just regular axial electrolytics with rubber seals, simply with a PCB each end that commons a few capacitors to make the final value, and then they are potted with a flexible encapsulant and an outer insulation sleeve to keep the terminals and board insulated from the case, and the leadouts are 2 short PTFE coated wires that are soldered to the inside of the terminals, and then the outer seal is low melting point solder for final seal after crimping the top on. They do not leak in use externally, but do lose vapour from the internal capacitor units into the housing, so they do fail by going high ESR and eventually nearly open circuit, but do not outgas at all from the case. Bloody expensive as well, and they were a pain, as the lead time was so long to get them. however those MSLH ones are slightly different in that they just take the rolled foil pack and flatten it ( so no lost mandrel construction like a regular electrolytic, these need a removeable mander in manufacture, a hand process to remove) then stuff it in a can, and laser or TIG weld it in a CA enclosure, and then use a vacuum fill to get the electrolyte in there, with a welded on fill port that is also a pressure vent ( weak point in the case for emergency vent). Will still have an operating life limit from degradation of the electrolyte with time and reforming though.