Hi OP, they can gift as much to you as they like in one go now, however the local authorities can request to see historic bank statements if they go into care and they may deem it that they gave you that money to avoid paying for long term care costs. (Though no idea why...)
The seven year rule another poster mentioned refers only to Inheritance Tax (which won’t apply anyway in your in-laws case as it sounds like their joint estate is under the IHT threshold of £650k for a married couple with no main residence).
PM me if you want to go into more detail. This is an area that