For the past few years I have made trips every few weeks with Ryanair to visit my mother in the UK. My bag weighs about 3 kg. All the necessary toiletries I keep at Mum's (not allowed to take larger bottles of liquids anyway), and I count off the exact number of knickers, pairs of socks (only in winter) and tops I shall need. Bra and jeans I wear for a few days longer than at home, reducing the need for spares in the luggage. As long as I've got my passport, purse with some Sterling in it, my tickets, phone and charger, anything I've forgotten I can get at the airport on arrival. Presents for my mother (usually flowers) I pick up at the airport, too.
I can't pack in advance because I won't remember I've packed it and I leave packing the absolute necessaries until right at the end to prevent panic attacks on the way to the airport.
If you're staying anywhere longer than 2 weeks, your bag shouldn't be any bigger than it would be for a few days, as surely you're going to have to wash things.
Back in the day, we went camping, and had the car full with absolutely everything including the sink. I had a list which I printed out* every year which went into several pages. There was never anything we didn't use, though.
I miss the fact that before leaving for our annual holiday, I would check through the entire contents of our medicine cabinet and throw out the old stuff and replenish it ready for the journey. When we got back, I would wash all the blankets to get the bits of grass and stuff off and to get them clean and fragrant for use in the house for the winter.
The main problem these days is that, having spent all those years with my head full of details and lists and the whereabouts of five people's belongings, I no longer any feel the joy or excitement in going away. Staying at home is far easier and I envy those of you who don't go on holiday.
*Well, way back in the early 80s I probably copied it out or xeroxed it.