Burn out light switch

[twin wheel camper]

My 1997 mk5 is burning out the main light stalk every few months
It is a chassis cab with 4 side marker and 2 rear marker lights all 5watt bulbs so pulling 30 watts.
It has always had these I didn't fit them, last year it started with sometimes when putting the lights on no dash lights but wiggling the stalk got them going but then it stopped working so I fitted a spare second hand I had which lasted rest of the winter but this winter it also has burned out to the extent that it smelled of burning plastic when switched on and on removing it 1 pin is melted and a no side,dash,tail,lights etc again so I put my last spare switch in and it's now after about 6 weeks playing up again so it's getting no more light stalks until I find the issue
Could it be the extra side marker lights and the roof corner light + all the rest putting the switch under to much load or is it likely to be a electric fault somewhere causing this all the lights are working but are old so could be corroded inside and putting the switch under to much load
Any help appreciated.

[Islander71]

It sounds to me there is likely a wire shorting to earth somewhere causing increase in current - more current (amps) = more heat. Corroded terminals in fittings unless shorting to earth would lower the current draw by increasing the resistance. Maybe a wire rubbing on metal stripping the wire's insulation off ?

[Keef]

You could run your extra lights through a relay which would drastically reduce the draw or maybe the headlight relay is faulty?

[twin wheel camper]

You could run your extra lights through a relay which would drastically reduce the draw or maybe the headlight relay is faulty?

Yea I'll probably just remove them and fit led lights then the problem should be over with providing that is the problem.
The headlights clearly use different pins,wires etc so they still work it's the dash,side marker lights,tail lights etc that are playing up.