If you are choosing to not take your car into Gib. Be aware there are new parking meters in all surrounding roads.
There is still an official presence should you have dificulties.
The machines show a max. duration stay of 2 hours. I have seen many "Denuncia" tickets on cars parked with 1 or 2 hour tickets.
After speaking to the official as to how we can park for 2 hours or more, he replied "Buy more tickets!". I didn't want to come out in 2 hours and feed the meter! "No no no, buy more tickets at the time you park up to the value of your duration!" So you want to stay 6 hours: Buy 3x2 hour tickets! "Do that and you won't get a denuncia from me!"
So there you have it, a Spanish way out of a beurocratic anomaly. Whether it is La Linea's intention to limit parking to 2 hours, god only knows but at least the official has found a way acceptable to him to enable you to park all day.
PS The machines didn't like 2€ coins despite saying they do!