Can I sponsor my siblings/his family more than 6 months prior to their planned visit

[baghloli]

Greetings,
I am planning on applying for visitors visa for my brother and his family (a total of 5 people, all are in Pakistan). They plan to visit next week in June/July. I am wondering whether applying 6 months in advance is possible/good idea. In past I have applied for my parents visa, and they were awarded 5 years multiple visit visas. I was also told that it is up to their discretion, and it is quite likely to get just 6 months visa. Shall I wait and sponsor them close to months of their visit. The only reason I dont wish to wait is because sometimes the clearance which is the pre-condition to this visa takes couple of months. What is your recommendations?
Also, Can I show 4 months of bank statements as proof of financial health. I moved most of the bank balance into brokerage six months ago and was left with under 1000 dollars in my checking account about 6 months ago. I do, though, have substantial amount in the brokerage account. and have about 25k in checking( i usually keep this amount in checking).

[immihelp]

1. It is a good idea not do get visa more than 2-3 months before traveling.
2. You can show money from any account you have.