Transitions 5 Ultimate will work in all versions of Vegas you have installed as well as any other NLE's supported by Transitions. It is a full retail product that will not expire in later versions.
I reckon your reply is far wiser than my question! Quite frankly you addressed my concerns and based on the content of your comment, you have experienced pretty much the same as me.
The killer phrase ... (assuming you really need those plugins)
Many thanks and happy clipping (my first camera was Super 8!)
I have upgraded to Vegas 18 Pro with Mercalli V5. V18 runs much more stable than Vegas 17, with almost no crashes. I am glad to be able to work quite stable and without crashes. The performance of the preview could be better.
The only problem I have is when I start Vegas and load a project, I sometimes have the problem that for some clips in the timeline the color grading is not "activated".
If I change something on the color wheels on the affected clip, it has no effect on the clip. Only when I make a minimal change to the color curve, all changes are activated at once. It also does not always affect the same clips, it is a kind of random principle.
* The media window scrubber in/out thing is frustrating to use and I haven't found a way to turn it off.
* The automatic multicam/audio sync tool has failed to produce a single correct result. Except once or twice I get that failure pop-up.
* Sometimes images on the timeline are rendered as black boxes in the preview. A mix of JPEGs and PNGs. These images are larger than the project's set resolution.
* The Hitfilm Movie Essentials plugins no longer work (I have past projects with the mosaic plugin... so I'm going to assume those are broken now). I've been considering buying PluralEyes, but will the $300 spent be worth it in the long run if Vegas can drop support for a given plugin whenever it feels like it?
Overall, it does feel a bit more prompt when editing, but things like the media window do seem to slow things down a bit to counteract that.
Hoping to eventually find some value in the upgrade expense...
mmm _ have V15 and was debating on upgrading and multicam/audio sync is very important to me
If you have VP17 you can use bundled Borix FX on VP18. However the new FX with version 18 will remove or disable older effects (at least bundled ones). It is either one or the other, apparently. And Boris cautions about this.