family visit visa 10yrs

[soumyanshu]

hi all
just wanted to get your expert opinion. I am embarking on a rather daring adventure of applying for 10yr family visit visa for my parents. i am british citizen. My parents have visited me four times in the past 10yrs, in 2008, 2012, 2014 and 2016 - each time staying between 4-5 months. Now i have a small child, they would need to come more regularly - once every year and it feels that 10yr visa should be ideal. in each of the past occassions we have applied successfully for 6 month visit visa and they have never overstayed and always left in line with their initial noted date of departure.
Given the "ongoing need" come to UK, previous positive history of visiting UK and the fact that they are settled in india with own property and pension, it feels this application should suffice all the criteria for 10yr visa. Having said that the home office is notorious for being opaque, constantly creates new rules and the current immigration environment is unfriendly to say the least.
i would like to know:
1. I would like to know from experts, if other than standard visitor visa application and providing rationale for them needing to come to UK for next 10yrs i should be providing anything else that can help the application.
2. i would also like to hear from any recent experience of successful or unsuccessful long term family visit visa stories and where they went right/wrong.
3. any other change in law/policy, whether public or non-public, that i should be concerned about?