5 year family visitor visa letter format

[aragon]

Hi,

I have just got ILR. My parents would like to apply for 5 year family visitor visa and I need help drafting their sponser letter.

They have been here in UK few times before on 6 months visitor visa and every time they returned home after 1-2 months of stay. Their last visa was for 2 years. Now I want them to apply for 5 years. They like to visit us every other year for couple of months.

How should I put this in words. Usually I just write that they like to visit us for few months and give the detail of the month they like to visit. But this time its different. Is it OK to write in the letter that they would like to visit us for few months every other year and I will pay for all their living and travelling cost.

If anyone has got any suggestions to this, please let me know. Its for the first time they are applying for a long term visitor visa and I want to make sure all goes well.

Thanks in advance.