Visitor Visa Enquiry - Long Term Application

[stitch]

Hello,
I am planning to apply 10-year visitor visa for my family. They have been to the UK six times before since 2012. Their last visa was for 2years.
My only worry is they don’t have enough funding in their bank accounts. They keep their money in a bank safe deposit and deposit some in their bank when needed. And sometimes, their bank account goes minus figures. They have another account and have £1400 to keep aside for this trip. Furthermore they have just deposited some amount into a new usd current account to show home office they have money. However, showing a big lump sum on a statement of a few days old account might be looked suspicious. I am also writing a letter that I will sponsor them and send my bank statements as well.
Would I be OK to apply since they have been here numerous times and I believe they are low risk?
Or should I go with 6 months visa this time and keep the money in the bank for a while and apply longer term visa next time?
Or should they keep the money there for a month, would it be enough to apply for 10 years visa?
Thanks in advance.

[Ticktack]

Hello,
I am planning to apply 10-year visitor visa for my family. They have been to the UK six times before since 2012. Their last visa was for 2years.
My only worry is they don’t have enough funding in their bank accounts. They keep their money in a bank safe deposit and deposit some in their bank when needed. And sometimes, their bank account goes minus figures. They have another account and have £1400 to keep aside for this trip. Furthermore they have just deposited some amount into a new usd current account to show home office they have money. However, showing a big lump sum on a statement of a few days old account might be looked suspicious. I am also writing a letter that I will sponsor them and send my bank statements as well.That would help cover the negatives.
Would I be OK to apply since they have been here numerous times and I believe they are low risk?That would be a fair assessment.
Or should I go with 6 months visa this time and keep the money in the bank for a while and apply longer term visa next time? You can go with the 10 years.
Or should they keep the money there for a month, would it be enough to apply for 10 years visa?6 months bank statement is required not a month.
Thanks in advance.