Easeus Todo backup

I use Easeus Todo, paid.
I have been backing up for a while but noticed some problems when I had to find a file. I used chatGPT and it said my method of back up could have problems so I'm simply asking for the best way to back up.

Here's what I need:
We do tax work so I need annual plus 3 months. I need the ability to go back 15 months. IF something really goes wrong there are ways to recover older items.
I need daily for 'OOPS HELP' happenings. I've had to go through backups 14-15 days old to find the file that was not pre-mangled.

GPT says I should keep all my current backups and do a new FULL backup and then incremental daily.

I've always browsed for needed backed up files and found the file I needed, but GPT says if I have to do a full restore and I have the original backup but not ALL the incremental then I'm in trouble, or at least getting a very time consuming recovery job.

Storage space is not a problem. I don't want massive back up files EVERY day though...they are BIG files.

What you should do is set up a schedule to automatically perform a system image backup monthly and daily incremental backups. The incremental backups would only be what changed in reference to the previous backup.
You should be able to specify how long to retain each backup set.
Or, if you want, you can setup to perform a file and folder backup, specifying which folders to backup. the same way. Full backup at the beginning of the month and daily incrementals.
I use Macrium Reflect, but looking at the user manual for Easeus Todo backup, you should be able to do the same. I do both system image and folder backups.

You do need all of the incremental backups as well as the initial full backup to restore a backup. A missing incremental will break the chain. A differential backup looks at the full backup and backs up everything that has changed. Only the last differential backup would be needed to restore.
You could do a full backup at the beginning of the month, daily incremental backups M-F, and a differential weekly. The weekly differential would cover the intervening incrementals. You would then need only retain the full backup and last differential each month to restore.
Incremental backups take less space and time to perform than a differential. Say you do a full backup on Monday. An incremental backup on Tuesday will look for changes made since Monday's backup and only backup the changes. An incremental on Wednesday will look at what changed since Tuesday and only backup the changes. The same with Thursday and Friday. To restore the backup, you need Monday's full backup and all incrementals on Tuesday, Wednesday, Thursday and Friday.
If you perform a differential backup on Saturday, it looks at what changed between Monday's full backup and backs up the changes. A differential backup a week later will look at the full backup for changes and backs up everything that changed. The second differential will take up more space and time than the first. To restore the backup you need the full backup and the second differential only.

One last thought. If you need to find a file from a previous backup, you can mount the image as another drive and search for the file,. You don't have to restore the the backup.

Image backups are not really the best solution for backing up data They are good for backing up OS/programs.

By nature of your business, you should be investigating data backup tools, with suitable redundancy.

I suggest you engage the services of a professional backup specialist who will analyse your systems, identify weakness and suggest robust solutions.

You may consider this to be expensive but data integrity is so extremely important to businesses, and the real question is "Can you afford not to invest?"